You'll never find a, b, c in the References if you don't do it
manually -- Word's solution was to add the title instead of to add
letters, even though no author-date system does it that way.
Note that the Book and other categories include a slot for "Short
Title" -- if you've entered something there, theb Word will use it
rather than the full item title, and in the case of a book with no
author, editor, or translator [it does happen], Word will use it for
the start of the bibliograpy entry. (In that case, if you _don't_ put
something in the "Short Title" box, it does something rather odd, but
it only happened to me once and I don't remember what it was.)
Note also that Word fails to insert "eds." after more-than-one editor
of a book when they appear in the Author position in a bibliography--
you get a blank between a comma and a period..