It seems to be mostly based on what Achler was talking about. I think you can find his work here: https://scholar.google.com/citations?view_op=view_citation&c

It seems to be mostly based on what Achler was talking about. I think you can find his work here: https://scholar.google.com/citations?view_op=view_citation&citation_for_view=XPjcqoAAAAAJ:ULOm3_A8WrAC https://scholar.google.com/citations?view_op=view_citation&c...