Analysis of the Case n=3 in Algebraic Cryptography with Involutory Key-Matrix and Known Alphabet. Jack Levine — 1964 Journal für die reine und angewandte Mathematik
Involutory commutants with some applications to algebraic cryptography. I. Jack Levine; Joel V. Brawley — 1966 Journal für die reine und angewandte Mathematik
Applications of Lie derivatives to symmetries, geodesic mappings, and first integrals in Riemannian spaces Gerald H. Katzin; Jack Levine — 1972 Colloquium Mathematicae