Citrix XenDesktop Handbook
http://virtualfeller.com/documents-2/citrix-xendesktop-handbook/
XenDesktop License Models Explained
http://support.citrix.com/article/CTX135501
As XenDesktop 5.6 introduces the Personal vDisk, please check the documents for Version 5.
http://www.citrix-links.com/xendesktop/xendesktop-5/xendesktop-5-scalability-architectual-design-guides/
Multi Region AWS CloudFormation Template for XenDesktop
http://blogs.citrix.com/2012/10/02/announcing-the-multi-region-aws-cloudformation-template-for-xendesktop/
35% improvement of VDI user density with HP ProLiant BL460c Gen8 & Citrix XenDesktop 5.6 & PVS 6.1
http://h30507.www3.hp.com/t5/Converged-Infrastructure/30-improvement-of-VDI-user-density-with-HP-ProLiant-BL460c-Gen8/ba-p/112409
Delivering Cisco Unified Communications with Citrix XenDesktop 5.6
http://blogs.citrix.com/2012/10/01/delivering-cisco-unified-communications-with-xendesktop/
XenDesktop : Best Practices with Cisco UCS
http://support.citrix.com/article/CTX135305
Citrix XenDesktop on NetApp Storage Solution Guide
http://rachelzhu.me/2013/04/19/citrix-xendesktop-on-netapp-storage-solution-guide/
XenDesktop 5.6 and NVIDIA GRID VGX
http://www.nvidia.com/object/xen-desktop.html