From the thesis abstract: "This thesis demonstrates an implementation of a parallel multilevel secure process. This is done within the framework of an electronic mail system. Security is implemented by GEMSOS [Gemini Standard Operating Systems], the operating system of the Gemini Trusted Computer Base. A brief history of computer secrecy is followed by a discussion of security kernels. Eventcounts and sequences are used to provide concurrency control and are covered in detail. The specifications for the system are based upon the requirements for a Headquarters of a hypothetical Marine Battalion in garrison."
Defense Technical Information Center (DTIC): http://www.dtic.mil/dtic/