problem-set/geometry/tarski/t13.desc created : 07/16/86 revised : 08/17/89 Natural Language Description : Theorem 13: If z1, z2, and z3 are each collinear with distinct points x and y, then z1, z2, and z3 are collinear. Versions : NOTE: all versions use a weighting scheme in which variables (and skolem functions) are weighted high and constants low. t13.ver1 : Original formulation of the axioms, from McCharen, Overbeek, & Wos [Aug. 1976], with lemmas about Collinearity added; uses hyperresolution, UR resolution, and unit deletion. created : 07/25/89. verified for ITP : Untested. translated for OTTER by : caw. verified for OTTER : 07/28/89. t13.ver2 : Reformulation of the axioms, from Quaife [JAR 5 (1989)]. created : 07/25/89. verified for ITP : Untested. translated for OTTER by : caw. verified for OTTER : no proof. t13.ver3 : Reformulation of the axioms, from Quaife [JAR 5 (1989)]. created : 07/25/89. verified for ITP : Untested. translated for OTTER by : caw. verified for OTTER : no proof.