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
I agree with U. Baur. This direct truncation is usually referred to as cross Gramian balanced truncation for which several extra research articles can be found. Hence, it should be called that way, or it should get a wiki page of its own. Either way some references are required. - P. Kürschner
I renamed the WX section to "Approximate Balancing" due to the Antoulas reference, please add a reference that introduces the term "Cross Gramian Balancing". Thanks. - C. Himpe