1. From racks to pointed Hopf algebras;Andruskiewitsch;Adv. Math.,2003
2. Zur Isotopie zweidimensionalen Flachen im R4;Artin;Abh. Math. Sem. Univ. Hamburg,1926
3. An infinite family of non-invertible surfaces in 4-spaces;Asami;Bull. London Math. Soc.,2005
4. Classifying 1-handles attached to knotted surfaces;Boyle;Trans. Amer. Math. Soc.,1988
5. J.S. Carter, M. Elhamdadi, M. Graña, M. Saito, Cocycle knot invariants from quandle modules and generalized quandle cohomology, Preprint