I prefer to add a wiki page for the cross Gramian approach and delete the direct truncation part (where does the name come from?) here. - U. Baur
OK with me. The source of the name I don't remember, I guess some talk, I have been using it for some time. It seems fitting, as without the balancing the truncation happens directly, thus my initial append of the BT article due to the close relation. - C. Himpe