Fixed several tiny (non-mathematical) typos

This pull request corrects several tiny typos. They are all non-mathematical, so probably do not need an entry in the errata list.

I added a few non-breaking spaces, only in places where it looked really necessary to do so in my particular printing (A4).

Merry Christmas!
I too was surprised that this fix was necessary; I thought that enclosing the capital letters by braces suffices to make them appear as capital letters in the output, but that doesn't seem to be the case.

Enclosing only the word suffices as well. (I don't know any advantages or disadvantages to enclosing the whole title.)