And-or graphs, theorem-proving graphs, and bi-directional search
–Classics/files/AI/classics/Machine_Intelligence_7/MI-7-Ch10-Kowalski.pdf
See also: Robert Kowalski. 1975. A Proof Procedure Using Connection Graphs. J. ACM 22, 4 (October 1975), 572-595.In B. Meltzer and D. Michie (Eds.), Machine intelligence 7. New York: Wiley, 167-194
Feb-1-1972