The chapter on Hydra in LevyBookCapabilityBasedComputerSystems can be found at:
* http://www.cs.washington.edu/homes/levy/capabook/Chapter6.pdf

A short summary of Hydra is at http://web.archive.org/web/20050308191259/http://www.stanford.edu/~emrek/quals/summaries/Hydra-Wulf-1974.txt.
----
ObjectCapabilityOperatingSystem CategoryOperatingSystem