Implementing Microsoft Windows Terminal Services, Capstone Project Example

Introduction

This Capstone project proposal will detail the implementation of a Microsoft Windows Server 2008 Terminal Services with Remote Applications (Apps) capabilities in the branch data center of a financial institution. The proposed server would consist of three servers with Terminal Services Gateway for session provisioning and Remote Apps to publish information from our data center to the remote branches. Technological advancements have revolutionized the way the way the world does business and, in order to stay competitive, small financial institutions need to make sure their customers have access to the latest technological services available at larger institutions. This necessitates knowing which server configuration would best suit the needs of the company. This paper will provide an evaluation of the benefits to using a Microsoft Windows Terminal Services over competing products such as Citrix XenApp, and VMWare ThinApp, as well as rationale for selecting Application virtualization over a similar technology such as VDI.

The right server configuration would enable a small financial institution to provide financial services to a myriad of remote device like personal computers, personal data assistants (PDAs), mobile phones, automatic teller machines (ATMs), external service providers, such as other branches, and individual teller stations within each branch (Zeanah et al., 2007). Windows’ high compatibility ratio over the majority of other servers and application management systems makes it the optimal choice for system management (Microsoft Corporation, 2008). This project will specifically examine the installation and configuration of the Remote Apps features of the Windows server configuration, including the security provisions and cost-effectiveness. This proposal will include the following chapters:

• Review of Other Work
• Rationale and System Analysis
• Project Goals and Objectives
• Project Deliverables
• Project Timeline and Milestones and
• Demonstrated Competencies

This service application pack will be implemented in Adirondack Bank (AB).

Review of Other Work

The extensive spread of cellular technology, the rapid growth of wireless technology, and the increasing use of such technologies in coordination with the internet or on a free standing basis to provide financial services in emerging markets necessitates the implementation of a proficient server to effectively handle the high volume of traffic from customers, employees, and business affiliates (Kellerman, 2002). According to Russinovich (2008) Windows Server 2008 is the most recent edition of the Microsoft server platform and it incorporates system level changes that covers all aspects of the operating system, including memory management, and provides the option for virtual computing. A strong server and well-managed database will allow users to easily store and retrieve information in a structured manner using a web interface (Ruth, 2009). Although there are a wide range of available server formats, such as Cisco IOS Network Security (IINS) and Linux, as well as the aforementioned Citrix XenApp and VMWare ThinApp, in order for global corporations to be successful, they require high-quality, up-to-date, well-maintained computer-based information systems capable of interfacing with PHP and MySQL, which are quickly becoming the default programs for rapid development of dynamic, database-driven web sites (Ruth, 2009; Stair &Reynolds, 2010). In addition to the high rate of compatibility with other hardware and software applications, the total cost of ownership and return on investment for Microsoft Windows Server 2008 Terminal Services, which includes the price of the software plus maintenance and profits gained from implementation, is the lowest and highest respectively amongst all other servers currently on the market (Price, 2004).

As demonstrated by the results obtained in the Microsoft Case Studies (2010a), employees of the Saudi Electric Company spent about 20% less time on maintenance following the implementation a more efficient Microsoft server platform. To cite a more domestic example, the Target Corporation integrated a Windows Server 2008 R2 Datacenter and Hyper-V at all of its stores and used Microsoft System Center data center solutions to manage more than 300,000 store-based endpoints (Microsoft Case Studies, 2011a). Target instigated the change gradually and, through the use of Microsoft Virtualization solution, the company will save millions of dollars in hardware, electrical, and maintenance costs (Microsoft Case Studies, 2011a). The benefits to such implementation also included reduced costs, increased the IT team’s ability to support the business, improved infrastructure management, and increased system availability (Microsoft Case Studies, 2011a). In addition, Target is using Microsoft System Center data center solutions, which allows the company to quickly deploy additional workloads, application upgrades, and security updates to the its vast network of stores nationwide (Microsoft Case Studies, 2011a). To complete this transition, Target Inc. incorporated Dell R710 hardware servers, Dell MD1000 units for storage, and Microsoft Services and Support, Datacenter Services, Windows Server 2008 R2 Datacenter, Microsoft System Center Configuration Manager 2007 R2, Microsoft System Center Operations Manager 2007 R2, Microsoft System Center Virtual Machine Manager 2008 R2, and Microsoft Hyper-V o provide software and services (Microsoft Case Study, 2008).

Using an example from a completely different business sector, Union Pacific is the largest North American railroad, connecting 23 western states with 32,100 miles of track and 8,400 locomotives (Microsoft Case Study, 2010b). With a customer base of 25,000 businesses in diverse markets, the railroad switched from VMware to the Windows Server 2008 R2 Datacenter Hyper-V technology to cost-effectively expand the use of virtualization to all production workloads and simplify management (Microsoft Case Study, 2010b). Through a gradual upgrade process, Union Pacific now has the ability to manage a growing virtual environment without increasing its staff (Microsoft Case Study, 2010b). Additional benefits include virtualization of production servers, significant hardware savings, easier server management, increased availability, and prompter response to business needs (Microsoft Case Study, 2010b). Union Pacific transitioned to the Dell PowerEdge R905 and 6950 servers with AMD Opteron processors for hardware, and Windows Server 2008 R2 Datacenter, Microsoft Hyper-V, Microsoft System Center Operations Manager 2007 R2, Microsoft System Center Virtual Machine Manager 2008 R2, and Microsoft System Center Configuration Manager 2007 R2 for software and services (Microsoft Case Study, 2010b). These case studies demonstrate the international flexibility of the Windows Server 2008 Datacenter models as well as the ability of the platform to suit all business needs.

The prowess of the Windows Server 2008 Datacenter has also been demonstrated in conditions similar to those that the system will encounter in its implementation in the AB. Jwaala, creator of the MoneyTracker online banking solution is a small business located in Austin, Texas and provides online personal finance management solutions for banks and credit unions so that they are able to provide a better online banking experience for their customers (Microsoft Case Study, 2010c). Jwaala was using the Ruby on Rails development system and the Linux, Apache, MySQL deployment stack to run its MoneyTracker application code and rewrote its MoneyTracker code using Microsoft Visual Studio 2008 and the Microsoft .NET Framework, including ASP.NET MVC and Language Integrated Query (LINQ) (Microsoft Case Study, 2010c). Implementation of this more efficient system produced benefits for the company including easier sales cycle, faster deployment, reduced need for customer support, efficient development environment, ease of interoperability (Microsoft Case Study, 2010c). Jwaala required the addition of Microsoft SQL Server 2008 Enterprise, Windows Server 2008 Enterprise, Microsoft Visual Studio 2008 Professional Edition, Microsoft .NET Framework 3.5, and Microsoft ASP.NET MVC in additional software and services and the incorporation of this system in this small financial institution proved to be strongly beneficial to the company.

To exemplify the true capabilities of the Microsoft Windows Server 2008 Terminal Services in a financial setting, the next example will demonstrate the use of the server in a larger banking institution. The ABN AMRO bank originated in 1720 when the first office was opened under the name Cordelois, De Vrijer & Mees and has grown into a large, global organization with 28,000 employees encompassing 27 countries and is responsible for the financial interests of more than 6,800,000 private customers and 400,000 commercial customers (Microsoft Case Study, 2011b). With such a large responsibility, the banking center requires a server capable of fulfilling a wide selection of requirements, including a sufficient platform which provides a rigid IT environment with modern web applications, a flexible and cost-efficient platform, and appropriate support through solution applications developed on the .NET platform (Microsoft Case Study, 2011b). The benefits of such implementation included automatic categorization of expenditure, depiction in graphs of income and expenditure, the ability to add other banks to the Financial Diary, budgeting by month or longer periods, integration of external applications in the internet banking environment, superior performance under high work pressure, and rapid and low-cost development of new services for customers (Microsoft Case Study, 2011b). Additionally, ABN AMRO customers gain insight into their financial situation with statements and graphs in the Financial Diary, a completely integrated .NET web application and the Financial Diary, which is an extra service for customers that allows them to see their expenditure patterns in the form of graphs and they can record expenditures in a predetermined budget (Microsoft Case Study, 2011b). ABN AMRO decided not to build the Financial Diary in its existing IT environment, but instead opted for a Microsoft .NET application, which can be integrated in the bank’s internet banking environment and the entire upgrade only required the addition of Microsoft SQL Server 2008 Enterprise and Microsoft .NET in additional software and services (Microsoft Case Study, 2011b).

In another example of the successful implementation of the Microsoft Windows Server 2008 Terminal Server within a financial institution, a major U.S. bank with hundreds of branch offices in six states and thousands of workers depends on its server infrastructure 24 hours a day, seven days a week to empower its IT team with centralized tools and applications that can resolve server problems remotely (Microsoft Case Study, 2008). However, accessing those tools was labor-intensive, time-consuming, and diminished IT response, so, to help simplify remote access, the bank deployed Windows Server 2008 Enterprise with Terminal Services (Microsoft Case Study, 2008). Through the Dell Longhorn Early Adopter Program for Windows Server 2008, IT staff can now connect to and launch applications in half the time, receive an identical interface, and have a consistent experience regardless of location (Microsoft Case Study, 2008). Installation of the Windows Server 2008 allowed the bank to streamline remote access, enhance security by restricting access to key administrative functions and reduce server downtime. The anticipated benefits include the completion of projects 20% faster, 50% quicker access to IT tools and applications, reduced bank employee downtime, enhanced security that is expected to reduce troubleshooting time, and the potential for expansion to other bank groups (Microsoft Case Study, 2008). The hardware implemented for the upgrade entails the Dell PowerEdge 2950 servers with quad-core Intel Xeon processors with Windows Server 2008 and Windows Server Remote Desktop Services included as software and services upgrades (Microsoft Case Study, 2008).

Rationale and Systems Analysis

Prior to the installation of a new server, it is necessary to first conduct a complete analysis of the current infrastructure and document the existing format, including the directory controls, resources, administrative controls, software requirements, and hardware requirements (Price, 2004). It is necessary to define the technical flow during the planning process, describing the decisions to be made and the commonly available options to consider in making the decisions and to relate the decisions and options to the business in terms of cost, complexity, and other characteristics (Microsoft Corporation, 2009). Framing the decision in terms of additional questions to the business ensures a comprehensive understanding of the appropriate business landscape and organizations that wish to make use of the new technologies need to account in their planning for the different business requirements that apply to individual users’ computing environments (Microsoft Corporation, 2009). Any particular environment can vary in both the types and degree of management controls that IT needs, and the types and degree of flexibility and access to resources that the user needs. In order to provide unique solutions for each situation, Microsoft has identified five core scenarios, which are Office Worker, Mobile Worker, Task Worker, Contract Worker, and workers who need to Access from Home to categorize users according to their work situations and computing demands (Microsoft Corporation, 2009).

These scenarios cover most desktop user situations, and describe the business requirements that apply to that situation, including both the individual user’s needs and the IT management needs, with the individual scenarios placing emphasis on different computer equipment, applications, security, and networking (Microsoft Corporation, 2009). These scenarios give IT a workable approach to optimizing the organization’s desktops without needing to customize desktops on an individual user basis (Microsoft Corporation, 2009). However, there is no ‘one size fits all’ when it comes to determining the computing needs of an organization and these needs will constantly change according to market trends, technological innovations, workforce size, organizational structural changes, and a wide array of other factors. As previously mentioned, there are other server applications that can be used comparable to that of Microsoft Windows Server 2008 Terminal Services, like Citrix XenApp, which is an on-demand application delivery solution that enables any Windows application to be virtualized, centralized, and managed in the datacenter and instantly delivered as a service to users anywhere on any device (Woodie, 2008). With more than 100 million users worldwide, XenApp provides proven application compatibility and, when compared to traditional application deployment technology, virtual application delivery with XenApp enables organizations to improve application management by centralizing applications in the datacenter to reduce costs, controlling and encrypting access to data and applications to improve security, and delivering applications instantly to users anywhere (Woodie, 2008).

The purpose of on demand virtual application delivery is that it allows for a single instance of an application to be managed in a hub within the datacenter and stream it to Windows PCs for offline use or run on high-powered servers in the datacenter for online use on any device or operating system. Whether application virtualization or session virtualization technology is used, XenApp ensures that users receive the highest quality experience through Citrix HDX technology, which adapts virtual application delivery and access based on each user’s device, network, and location to ensure an optimal experience (Woodie, 2008). XenApp enables enterprise class scalability for any size business and ensures that virtual application delivery and management is secure by design. XenApp integrates the tools and infrastructure needed to help control, measure, and monitor performance to ensure that service level agreements and corporate security requirements are met. Application virtualization technology, session virtualization technology, and centralized application management gives users direct access to Windows applications from any device, using a web browser via Citrix Receiver. Citrix Receiver delivers applications to over 30 operating systems (Woodie, 2008).

Many companies that were set up according to trend of the late 1980s that made it cost effective to distribute computing and client/server models, which resulted in data centers filled with underutilized hardware resources causing an inefficient use of floor space and excessive power consumption in the data center (Tuhkanen, 2010). Virtualization through physical to virtual server consolidation provides a solution to “server sprawls” where several physical servers are migrated to operate on top of single server hardware using a Windows Server 2008 virtual machine that is running on top of VMware ESXi 3.5 virtualization platform (see Figure 1) (Tuhkanen, 2010). VMware ESXi 3.5 virtualization platform allows the user to reduce hardware requirements, increase hardware utilization, and increase energy efficiency with the highest server consolidation ratios, commonly exceeding ten virtual machines per physical processor (VMware, 2012). Conversion to a virtual platform also reduces the required datacenter square footage, rack space, power, cooling, cabling, storage and network components by decreasing the number of physical machines and further increases the consolidation ratio by leveraging VMware’s unique memory management capabilities and load-balancing features included in VMware ESX and VMware ESXi (VMware, 2012). Conversion to a virtual server also reduces the complexity of hardware management through comprehensive virtualization of server, storage and networking hardware (VMware, 2012).

Figure 1: Server Virtualization

(Tuhkanen, 2010)

Virtualization provides computing resources as pools, thus decoupling hardware and software. A virtual machine is a guest operating system that shares the underlying physical hardware with other virtual machines running on top of the same physical host. Each virtual machine has its own operating system and virtual hardware provided by the host, so each virtual machine is independent and completely separated from other virtual machines. Four main forms of virtualization are server, storage, network, and application virtualization. Each form represents an abstraction from physical environments in different manner. Although virtualization is commonly considered as a way of partitioning multiple resources into a single hardware entity, like in server virtualization, it can also do just the opposite: representing multiple hardware instances as a single computing resource. This form of virtualization is often utilized in storage, network and application virtualization approaches. Server virtualization is the most common approach and generally when the term “virtualization” is discussed, indeed people are referring to server virtualization (Tuhkanen, 2010).

Project Goals and Objectives

In the current climate of blended threats, where malicious software exploits vulnerabilities from the kernel and extends through all other applications, a security strategy must include a combined effort that extends beyond the OS (operating system) and network to other areas such as desktop applications like Microsoft Office and Internet browsers. Windows Server 2008 offers more server roles, flexibility, security, and manageability than all previous Microsoft server operating system (Palmer, 2009). Adirondack Bank has recently begun to offer Internet banking and intends to deliver these services using a solid security framework that protects customers’ and the institution’s information from intruders (Adirondack Bank, n.d.). To achieve this purpose, AB is committed to working with Internet service and communications providers to create the safest operating environment possible for customers, integrating multiple levels of security, including cryptography and Secure Sockets Layer (SSL) protocol, which uses a highly effective cryptography techniques to ensure that the information being passed is authentic, cannot be deciphered, and has not been altered en route (Adirondack Bank, n.d.). SSL also utilizes a digitally signed certificate once a secure connection has been established between the customer’s browser and the server, which ensures that the user is communicating with the Online Banking Server and not a third party trying to intercept the transaction (Adirondack Bank, n.d.).

The customer must provide a valid User ID and Password to gain access to the services and this information is encrypted, logged by the server forming another complete physical security layer to protect the server’s information, and a request to log on to the system is processed (Adirondack Bank, n.d.). Although SSL uses established cryptography techniques, session time-outs and a limit on the number of logon attempts are examples of other security measures in place to ensure that inappropriate activity is prohibited (Adirondack Bank, n.d.). AB additionally recommends that customers adhere to the following recommendations, which are to:

1. Use the most recent 128 bit-encryption version of either Netscape Navigator or Microsoft Internet Explorer for optimal viewing and security
2. Keep your password confidential and follow protocols outlined on the website to choose a strong password
3. Keep your computer free of viruses, use virus protection software to routinely check for a virus on your computer, and never allow a virus to remain on your computer while accessing the online banking system

The AB server also seeks to protect information and network access through the use of firewalls, filtering routers, and the trusted operating system and all transactions sent to the Banking Server must first pass through a filtering router system that will automatically direct the request to the appropriate server after ensuring the access type is through a secured browser and nothing else (Adirondack Bank, n.d.). The function of the routers will be to verify the source and destination of each network packet to manage the authorization process of letting packets through while prohibiting all other types of Internet access methods at this point, blocking all non-secured activity and defending against inappropriate access to the server (Adirondack Bank, n.d.). Afforded the protection of the most up to date firewall platform, the Banking Server is protected against system intrusions and effectively isolates all but approved customer financial requests, secures the hardware running the Online applications and prevents associated attacks against all systems connected to the Banking Server with around the clock monitoring for a wide range of anomalies to determine if attempts are being made to breach the security framework (Adirondack Bank, n.d.). Once authenticated, the customer is allowed to process authorized Internet banking transactions using host data and the Internet banking services, processed securely and communication time-outs ensure that the request is received, processed, and delivered within a given time frame, ensuring that foreign attempts to delay or alter the process will fail (Adirondack Bank, n.d.). The competitiveness of the current global market emphasizes that the need for computing power and flexibility are many, particularly when the requirement of efficiency in resource use is considered.

The goals for Adirondack Bank include:

• Increasing compliance with security, privacy, and auditing requirements by centralizing data and securing the desktop
• Meeting user expectations for a flexible, mobile workplace
• Rapidly deploying and removing desktop environments for temporary staff on and off premise in a secure and expedient manner
• Extending the usability of older hardware to avoid the discarding of electronics into landfills which is harmful to the environment

In order to use Windows Server 2008, it is first necessary to make sure the Adirondack Bank meets the following hardware requirements:

• “Minimum Processor: 1GHz (x86 processor) or 1.4GHz (x64 processor) Recommended: 2GHz or faster Note: An Intel Itanium 2 processor is required for Windows Server 2008 for Itanium-based Systems
• Minimum Memory: 512MB RAM • Recommended: 2GB RAM or greater Maximum (32-bit systems): 4GB (Standard) or 64GB (Enterprise and Datacenter) Maximum (64-bit systems): 32GB (Standard) or 2TB (Enterprise, Datacenter and Itanium-based Systems)
• Minimum Available Disk Space: 10GB Recommended: 40GB or greater Note: Computers with more than 16GB of RAM will require more disk space for paging, hibernation, and dump files
• DVD-ROM drive Display and Peripherals: Super VGA (800 x 600) or higher-resolution monitor, Keyboard, Microsoft Mouse or compatible pointing device” (Petri, 2009)

The multiple applications for Windows Server 2008 can also be installed as a Server Core installation, which is a diminished version of Windows excluding the Windows Explorer GUI, which requires manual configuration through the command line interface or remotely using a Microsoft Management Console (MMC) (Kellerman, 2002). The Server Core can be used for dedicated machines with basic roles like Domain controller/Active Directory Domain Services, DNS Server, DHCP Server, file server, print server, Windows Media Server, IIS 7 web server and Windows Server Virtualization virtual server (Kellerman, 2002).

Project Deliverables

This portion of the project will provide documentation regarding Microsoft’s minimum and recommended hardware requirements for the elements being implemented in the server upgrade process. In addition, this section will provide instructions for the installation of the server as well as all of the accompanying components. The functions of the software and hardware will be itemized and the systems functions will be documented and analyzed in comparison with the functionality of the previous system. Based on the configuration of the last server, this newly implemented configuration will be assessed after 24 hours, three, seven, 14, 30, 60, and 90 days with detailed system analyses compiled and scrutinized to determine the efficacy, appropriateness, and benefits of the new system with reports prepared indicating how the new system operates in comparison to the previous format.

Project Timeline with Milestones

Competency Matrix 

References

Adirondack Bank. (n.d.). Security information: Online security protection. Retrieved from https://www.adirondackbank.com/ab-sOnline.aspx

Bart Jacob, David Janson, Oliver Mark, Fabio L Marras (2002, December). Linux and Branch Banking. International Business Machines (IBM) Corporation International Technical Support Organization. Retrieved from ibm.com/redbooks

Kellerman, T. (2002, May). Mobile risk management: E-finance in the wireless environment. The World Bank. Retrieved from http://www1.worldbank.org/finance/assets/images/mobile_risk_management.pdf

Microsoft Case Study. (2008, April 28). Major US Bank: Bank Speeds Remote Access Connection Time by 50 Percent, Boosts IT Help-Desk Response. Retrieved from http://www.microsoft.com/casestudies/Case_Study_Detail.aspx?CaseStudyID=4000001873

Microsoft Case Studies. (2010a). Saudi Electricity Company: Electric company powers IT, adopts operations framework through services engagement. Retrieved from http://www.microsoft.com/casestudies/Microsoft-Services/Saudi-Electricity-Company/Electric-Company-Powers-IT-Adopts-Operations-Framework-Through-Services-Engagement/4000007797

Microsoft Case Studies. (2010b, December 9). Union Pacific: Union Pacific reduces costs, boosts IT responsiveness with Hyper-V. Retrieved from http://www.microsoft.com/casestudies/Case_Study_Detail.aspx?CaseStudyID=4000008816

Microsoft Case Study, (2010c, March 10). Jwaala Online Banking Solution Benefits after ASP.NET MVC Replaces Ruby on Rails, Linux. Retrieved from http://www.microsoft.com/casestudies/case_study_detail.aspx?casestudyid=4000006675

Microsoft Case Studies. (2011a, March 17). Target: Large retailer relies on a virtual solution to deliver optimal shopping experience. Retrieved from http://www.microsoft.com/casestudies/Case_Studies_Detail.aspx?CaseStudiesID=4000009407

Microsoft Case Study. (2011b, June 12). ABN AMRO Private Bank. Retrieved from http://www.microsoft.com/casestudies/Microsoft-SQL-Server-2008-Enterprise/ABN-AMRO/ABN-AMRO-customers-gain-insight-into-their-financial-situation-with-statements-and-graphs-in-the-Financial-Diary-a-completely-integrated-.NET-web-application/4000010252

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Microsoft Organization. (2009, June). Solution Accelerator: Infrastructure Planning and Design (IPD). Microsoft Corporation. Retrieved from http://www.microsoft.com/technet/SolutionAccelerators

Palmer, M. (2009). Hands-On Microsoft Windows Server 2008. Boston: Cengage Learning. Retrieved from http://www.ichapters.com/shop/content/palmer02343_1423902343_01.01_toc.pdf

Paquet, C. (2009). Implementing Cisco IOS Network Security (IINS). Cisco Systems, Inc. Indianapolis, IN: Cisco Press

Petri, D. (2009, January 8). How to Install Windows Server 2008 Step by Step. Petri IT Knowledgebase. Retrieved from http://www.petri.co.il/how-to-install-windows-server-2008-step-by-step.htm#

Russinovich, M. (2008, March). Inside Windows Server 2008 kernel changes. TechNet Magazine. Retrieved from www.microsoft.com/uk/technetmagazine

Ruth, A. (2009, April). Design and development of an inline database system for banks using MySQL and PHP. PGD/MCS/2007/1221. A project submitted to the Federal University of Technology, Minna, in partial fulfillment of the requirement for the award of the postgraduate diploma in Computer Science.

Smith, R.F. (2003, February-May). Develop a Secure Infrastructure with Microsoft’s Security Guidance. Microsoft Security Watch.

Stair, R. & Reynolds, G. (2010). Principles of Information Systems, A Managerial Approach, (9^th ed.).

Tuhkanen, A. (2010, April). Server Consolidation with VMware ESXi 3.5. Bachelor’s Thesis

Degree programme in Information Technology. Retrieved from https://publications.theseus.fi/bitstream/handle/10024/12658/Thesis_Aki_Tuhkanen.pdf?sequence=1

VMware. (2012). VMware infrastructure. VMware, Inc. Retrieved from http://www.vmware.com/products/vi/overview.html

Woodie, A. (2008, August 27). Citrix Addresses Performance with XenApp 5. The Windows Observer, 6(31). Retrieved from http://www.itjungle.com/two/two082708-story01.html

Zeanah, J. et al. (2007, October 25). United States patent application publication. Retrieved from http://www.google.com/url?sa=t&rct=j&q=zeanah%20patent%20publication%202007&source=web&cd=2&sqi=2&ved=0CCYQFjAB&url=http%3A%2F%2Fwww.google.com%2Fpatents%2FUS20070250808.pdf&ei=BWBKT9t65diIAs3K5dwN&usg=AFQjCNHWzaBjil79iLDSehqiEICnrKPfeg