TFS Security Question: How to remove Windows groups in 2013

Hello,

I know I must be missing something simple here.  I've been a TFS administrator for years.  In 2010, it was easy to add or remove Windows groups.  In 2013, I see how to add a Windows group (From Team Explorer, select Group Membership, click on Add and select 'Windows User or Group'), but where is the option for removing Windows groups in TFS 2013?

Thanks in advance.