1. J.W. Alexander, Topological invariants of knots and links. Trans. Am. Math. Soc. 30, 275–306 (1928)
2. J.W. Alexander, Letter to Oswald Veblen, 1919, Papers of Oswald Veblen, 1881–1960 (bulk 1920–1960), in Archival Manuscript Material (Collection), Library of Congress
3. M.M. Asaeda, J.H. Przytycki, Khovanov homology: torsion and thickness, in Proceedings of the Workshop, “New Techniques in Topological Quantum Field Theory” Calgary/Kananaskis, Canada, August 2001, ed. by J.Bryden,
http://front.math.ucdavis.edu/math.GT/0402402
4. G. Birkhoff, On the structure of abstract algebras. Proc. Camb. Philos. Soc. 31, 433–454 (1935)
5. J.S. Carter, M. Elhamdadi, M. Saito, Homology theory for the set-theoretic Yang-Baxter equation and knot invariants from generalizations of quandles. Fund. Math. 184, 31–54 (2004),
http://front.math.ucdavis.edu/0206.5255