1. Digernes, T.: Duality for weights on covariant systems and its applications. Thesis, University of California, Los Angeles 1975
2. Landstad, M. B.: Duality theory for covariant systems. Preprint Univ. of Trondheim 1974
3. Nakagami, Y.: Duality for crossed products of von Neumann algebras by locally compact groups. Bull. AMS81, 1106–1108 (1975)
4. Nakagami, Y.: Dual action of a von Neumann algebra and Takesaki's duality for a locally compact group. Preprint University of Kyushu 1975
5. Roberts, J. E.: Cross products of von Neumann algebras by group duals. Proc. of the meeting onC⋆-algebras and their applications to theoretical physics, Roma, March 1975. (To be published in Symposia Mathematica. London: Academic Press)