[1] B\"{o}hm G, Brzezi\'{n}ski T. Cleft extensions of Hopf algebroids. Appl Categor Structure, 2006, 14: 431--469

[2] B\"{o}hm G, Nill F, Szlachanyi K. Weak Hopf algebras I: Integral theory and $C^{\ast}$-structure. J Algebra, 1999, 221: 385--438

[3] Blattner R, Cohen M, Montgomery S. Crossed product and inner actions of Hopf algebras. Trans Amer Math Soc, 1986, 298: 671--711

[4] Blattner R, Montgomery S. Crossed product and Galois extensions of Hopf algebras. Pacific Journal of Math, 1989, f 137: 37--54

[5] Caenepeel S, De Lombaerde M. A categorical approach to Turaev's Hopf group-coalgebras. Comm Algebra, 2006, f 34: 2631--2657

[6] 刘玲, 王栓宏. 构造群缠绕模范畴成为辫子张量范畴. 数学物理学报, 2010, 30A(6): 1612--1620

[7] Shen B L, Wang S H. Blattner-Cohen-Montgomery's duality theorem for (weak) group smash products. Comm Algebra, 2008, 36: 2387--2409

[8] Shen  B L, Wang S H. On group crossed products. Int Electron J Algebra, 2008, 4: 177--188

[9] Turaev V. Homotopy field theory in dimension 3 and crossed group-categories. 2000, Preprint arxiv: math GT/0005291

[10] Virelizier A. Hopf group-coalgebras. J Pure Appl Algebra, 2002, 171: 75--122

[11] Van Daele A, Wang S H. New braided crossed categories and Drinfel'd quantum double for weak Hopf group coalgebras. Comm Algebra, 2008, 36: 2341--2386

[12]  Wang S H. Group twisted smash products and Doi-Hopf modules for T-coalgebras.Comm Algebra, 2004, 32(9): 3417--3436

[13] Wang S H. Morita contexts, π-Galois extensions for Hopf π-coalgebras. Comm Algebra, 2006, 34: 521--546

[14] Zunino M. Double construction for crossed Hopf coalgebra. J Algebra, 2004, 278: 43--75

[15] Zunino M. Yetter-Drinfeld modules for crossed structures. Journal of Pure and Applied Algebra, 2004, 193: 313--343