・Slightly modified the notation of the discussion surrounding the second and third
　displays of \S 2.11 (by replacing certain instances of "l" by "l'", in order to
　avoid confusion)

・Added some explanatory text to the discussion immediately preceding the second to
　last display of \S 2.11 

・Corrected a misprint in the second to last sentence of the paragraph immediately 
　preceding Example 2.12.1 ("-modules" ---> "-monoids")

・Corrected a misprint in the second sentence of Example 2.13.1, (i) ("X" ---> "X^{cp}")

・Corrected a misprint in the third sentence of Example 2.14.3 involving "\eta"