WPF (MVVM): Closing a view from Viewmodel?

http://stackoverflow.com/questions/1484233/wpf-mvvm-closing-a-view-from-viewmodel

http://stackoverflow.com/questions/501886/how-should-the-viewmodel-close-the-form/3329467#3329467

http://www.japf.fr/2009/09/how-to-close-a-view-from-a-viewmodel/