1. N. Andruskiewitsch, M. Graña, From racks to pointed Hopf algebras, to appear. math.QA/0202084.
2. J.S. Carter, M. Elhamdadi, M. Saito, Twisted quandle cohomology theory and cocycle knot invariants, math.GT/0108051.
3. Quandle homology groups, their Betti numbers, and virtual knots;Carter;J. Pure Appl. Algebra,2001
4. J.S. Carter, M. Saito, Quandle homology theory and cocycle knot invariants, math.GT/0112026.
5. C. Chevalley, Théorie des groupes de Lie. Tome III. Théorèmes généraux sur les algèbres de Lie, Hermann & Cie, Paris, 1955.