Books on early reptilian evolution

["Robert Karn" <rkarn@butler.edu>]

Hello,
        I've just been added to this list and would like to ask a question
to the seasoned users.  As a preamble to my question, I should say that I
am not a paleontologist but have had a long term interest in dinosaurs and
teach a course on the subject at the introductory level.  I would like my
students to get a better background in early reptilian evolution,
particularly that period where the first dinosaurs appeared upon the
scene.   My question is:  can anyone recommend a book(s) that covers this
area and that would be appropriate for undergraduate university students?
Thanks in advance,
Bob Karn