(Miller06) – M. S. Miller, “Robust Composition: Towards a Unified Approach to Access Control and Concurrency Control,” 2006. archive 
The object-capability model was first proposed by Jack Dennis and Earl C. Van Horn in 1966. [3]
[3] J.B. Dennis, E.C. Van Horn. “Programming Semantics for Multiprogrammed Computations.” Communications of the ACM, 9(3):143–155, March 1966.
The Ports as the basis of an Object-Capability Model on the Web section of the spec is a useful read. page