szasz, 1963, Introduction to Lattice Theory
birkhoff, 1967, Lattice Theory, xxv
preston, 0, The lattice dimension of a class of graphs
10.1090/S0002-9947-1937-1501929-X
10.1016/S0020-7373(75)80029-0
chandrasekaran, 1972, Frontiers of Pattern Recognition
koffka, 1950, Principles of Gestalt Psychology