[1] Beattie M, Dˇascˇalescu S, Gr¨unenfelder L. Constructing pointed Hopf algebra by Ore exten-sions. J Algebra,
2000, 225: 743–770

[2] Kassel C. Quantum Groups. New York: Springer-Verlag, 1995

[3] Li F. Weak Hopf alg ebras and some new solutions of quantum Yang-Baxter equation. J Algebra, 1998, 208: 72-100

[4] Li F, Cao H J. Semilattice graded weak Hopf algebra and its related quantum G-double. J Math Physics, 2005, 46(8): 1–17

[5] Li F, Cao H J. Semilattice graded weak Hopf algebra and its quantum double//Advance in ring theory proceedings. 2005: 139–150

[6] Li F, Duplij S. Weak Hopf algebras and singular solutions of quantum Yang-Baxter equation. Comm Math Phys, 2002, 225: 191–217

[7] Li F, Zhang Y Z. Quantum Doubles From A Class of Noncocommutative Weak Hopf Algebras. J Math Physics, 2004, 45(8): 3266–3281

[8] Lin B I P. Semiperfect coalgebra. J Algebra, 1977, 49: 357–373

[9] McAlister D B. Characters of finite semigroups. J Algebra, 1972, 22: 183–200

[10] Montgomery S. Hopf algebras and their actions on rings//CBMS Regional Conference Series in Mathematics.
Providence. RI: American Mathematical Society, 1993: 82

[11] Montgomery S. Indecomposable coalgebras, simple comodules, and pointed Hopf algebras. Proceeding of
American Mathematical Society, 1995, 123(8): 2343–2351

[12] Petrich M. Inverse Semigroups. New York: John Wiley & Sons, 1984