Capability-Based Computer Systems - - Henry M. Levy; Digital Press, 1984, ISBN 0932376223. Thorough survey and description of early capability and object based hardware and software systems. Out of print, available as free download, PDF format.
KeyKOS - - Persistent, pure capability, nanokernel OS, for IBM S/370 mainframe systems, by Key Logic, Inc. Influenced design of other capability OSs, notably EROS and successors. Set of papers, notes, patents, bibliography.