ACKNOWLEDGMENT

The work was started during my visit of Macquarie University (Sydney, Australia) and was completed in Max-Planck-Institut für Mathematik (Bonn, Germany). I would like to thank these institutions for hospitality and inspiring atmosphere. Special thanks to Prof. Ross Street who pointed out to me the references [7] Skandalis, Georges. 1990. Operator algebras and duality. Proceedings of the International Congress of Mathematicians. 1990, Kyoto. Vol. II, pp.997–1009. Math. Soc. Japan, Tokyo, 1991 [Google Scholar], [1] Baaj, Saad and Skandalis, Georges. 1993. Unitaires multiplicatifs et dualite pour les produits croises de C^*-algebres. Ann. Sci. Ecole Norm. Sup. (4), 26(4): 425–488. [Crossref] , [Google Scholar] and explained his own work [8] Street, Ross. 1998. Fusion operators and cocycloids in monoidal categories. Appl. Categ. Structures, 6(2): 177–191. [Crossref], [Web of Science ®] , [Google Scholar].