1. Alexandroff, Paul, Sur les espaces discrets, Comptes Rendus, vol. 200 (1936), pp. 1649-1651.
2. Semi-Serial Order;Bennett, Albert A.;Amer. Math. Monthly,1930
3. Birkhoff, Garrett, On the combination of subalgebras, Proceedings of the Cambridge Philosophical Society, vol. 29 (1933), pp. 441-464.
4. On the Lattice theory of ideals;Birkhoff, Garrett;Bull. Amer. Math. Soc.,1934
5. Dedekind, R., Stetigkeit und irrationale Zahlen, authorized translation entitled Essays on Number, Chicago, Open Court, 1901.