How to delete Microsoft .NET Portable Library Reference Assemblies 4.6

The Microsoft .NET Portable Library Reference Assemblies 4.6 is a set of reference assemblies that can be used to compile .NET source code as a Portable Class Library (PCL). PCL libraries can be used in many apps and across platforms, such as Windows Phone, Windows Store and Windows Azure. It is the same set that is used in Visual Studio 2013.