J. Andersen, A. Bene, and R. Penner. (2007)cite arxiv:0710.2651
Comment: 24 pages, 4 figures Theorem 3.6 has been strengthened, and Theorems
8.1 and 8.2 have been added.
R. Jullig, and F. De Remer. ACM SIGPLAN '84 Symp. on Compiler Construction, ACM press, Montréal, Published as ACM SIGPLAN Notices, volume 19, number 6.(June 1984)