remove duplicate surfaces or brep

Hi,
As i said in the title i'm trying to remove duplicate surfaces from a list.I read discussions about how remove duplicate points,(http://www.grasshopper3d.com/forum/topics/filter-out-duplicate-numbers).here i found a definition by David Rutten.But it doesn't work for surfaces...so do you know a way to do this?
Thank you very much

Regards

Paolo