[1] Boca I. A central theorem for Hopf algebras. Comm in Alg, 1997, 25(8): 2593-2606

[2] B¨ohm G, Nill F, Szlach´anyi K. A coassociative C-quantum group with nonintegral dimensions. Lett
Math Phys, 1996, 35: 424-437

[3] B¨ohm G, Nill F, Szlach´anyi K. Weak Hopf algebras I. Integral theorey and C-structure. J Alg, 1999,
221: 385-438

[4] D?asc?alescu S, Raianu S¸, Zhang Y H. Finite Hopf-galois coextensions, crossed coproducts, and duality. J
Alg, 1995, 178: 400-413

[5] Li F. Weak Hopf algebras and some new solutions of the quantum Yang-Baxter equation. J Alg, 1998,
208: 72-100

[6] Li F. Weak Hopf algebras and regular monoids. Journal of Mathematical Research and Exposition. 1999,
19: 325-331

[7] Molnar R K. Semi-direct product of Hopf algebras. J Alg, 1977, 47: 29-51

[8] Montgomery S. Hopf Algebras and Their Actions on Rings. CBMS, Lect Notes, 1993