Books  Books 1  1 of 1 on V there must be a third element in each of the mclasses AB, BC, CA, and by Assumption.... 
V there must be a third element in each of the mclasses AB, BC, CA, and by Assumption II these elements must be distinct from each other and from A, B, and C. Let the new elements be D, E, G, so that each of the triples ABD, BCE, CAG belongs to the same... Projective Geometry  Page 4 by Oswald Veblen, John Wesley Young  1910 Full view 
