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    "Control Predicates Are Better Than Dummy Variables For Reasoning About 
        Program Control."
    Leslie Lamport.
    May 5, 1986.  19 pages.

Author's Abstract

    When explicit control predicates rather than dummy variables are
    used, the Owicki-Gries method for proving safety properties of
    concurrent programs can be strengthened, making it easier to
    construct the required program annotations.