1. Zur Axiomatik der Elementargeometrie;Bergmann, Gustav;Monatsh. Math. Phys.,1929
2. American Mathematical Society Colloquium Publications, Vol. 25;Birkhoff, Garrett,1948
3. A characterization of Boolean algebras;Birkhoff, Garrett;Ann. of Math. (2),1939
4. Free lattices;Whitman, Philip M.;Ann. of Math. (2),1941
5. Free lattices. II;Whitman, Philip M.;Ann. of Math. (2),1942