I am building a new server and plan to install Windows Server 2008 R2 Enterprise. I will create multiple virtual machines using Hyper-V. Each virtual machine will be installed with Windows Server 2008 R2 Standard. Do I need separate Windows Server 2008 R2 Standard licenses for each virtual machine that I create? I can't find any good documentation on this. Links to an official Microsoft website with explanation of the licensing would be appreciated!