The paper introduces formally the concept of local factorizability used in earlier factorizability work, identifies the basic form of obstructions to local factorizability of birational morphisms, and outlines a combinatorial technique for analyzing such obstructions. As an application and illustration, two open cases in the classification of birational morphisms with small canonical divisors are settled.
"Combinatorial analysis of point obstructions to local factorizability in three-folds." Hokkaido Math. J. 18 (3) 397 - 458, October 1989. https://doi.org/10.14492/hokmj/1381517730