Spell checks

[davidvandebunte]

Spell check "contradition" in Chp 17.

Spell check "subroof" in Chp 18.

Spell check "apropriate" in Chp 42.

In Chp 43 the following sentence has an unmatched bracket, besides being otherwise hard to read:

In fact, we could have added rule R5 to T alone, and leave out rule R5)

In Chp 30, replace "just in case" with "if":

and stipulate that ‘R(x,y)’ is to hold of x and y just in case there is an arrow running from x to y in our diagram.

[rzach]

Thanks!