Chord Theory Book

Hi Lee,

I just bought your book which is very good. Iam interested in jazz music, not because Iam deeply in love with jazz music, but because I admire the musical knowledge and technique that jazzers have. Could you please direct me to a source which deals with parallel major/minors and sub-dominants  and how they are used? This is not covered in your book , for understandable reasons, but I would like to fill this gap in my knowledge and be able to apply these concepts  to the music I really do love.

Many thanks.