Lata Narayanan Jaroslav Opatrny Dominique Sotteau All-to-All Optical Routing in Chordal Rings of Degree 4. 155-178 2001 31 Algorithmica 2 http://link.springer.de/link/service/journals/00453/bibs/1031002/10310155.html db/journals/algorithmica/algorithmica31.html#NarayananOS01