1. American Mathematical Society Colloquium Publications, Vol. 25;Birkhoff, Garrett,1948
2. Lattices with unique complements;Dilworth, R. P.;Trans. Amer. Math. Soc.,1945
3. The word problem for abstract algebras;Evans, Trevor;J. London Math. Soc.,1951
4. Free unions of lattices;Sorkin, Yu. I.;Mat. Sbornik N.S.,1952
5. Free lattices;Whitman, Philip M.;Ann. of Math. (2),1941