Primary Literature by Jonathan Marks
Benveniste, Raoul E. and Todaro, George J. (1976) Evolution of type C viral genes: Evidence for an Asian origin of man. Nature, 261:101-107. This study also applied DNA hybridization to the apes. They found a 3-way split.
socrates.berkeley.edu/~jonmarks/biblio.html
Link seems to be outdated, and Nature still has the full text embargoed. The only thing I found related:
http://www.pnas.org/content/pnas/71/11/4513.full.pdf