I added the following text to explain the notation used in procedure
signatures:

    Parameters given in square brackets are optional. Unless otherwise noted
    in the text describing the procedure, any number of these optional
    arguments may be supplied, from zero to the full list. When a procedure
    returns multiple values, this is shown by listing the return values in
    square brackets, as well. So, for example, the procedure with signature

	halts? f [x init-store] -> [boolean integer]

    would take one, two or three input parameters, and returns two values.

Marc F will find this an inadequate stopgap measure, but I just cannot
go through four large documents of text, two of them larded up w/HTML
markup, and change every occurrence over to some alternate notation at
this late date. It seems readable enough to my eye...
    -Olin