Daniel Edwards asks an excellent question regarding theory journals to search for good articles about your subject. Here are some that I have found useful:
Music Theory Online - convenient, because it's a web journal
Music Theory Spectrum - also on JSTOR
Journal of Music Theory - also on JSTOR
19th Century Music - on JSTOR; a little more on the musicological side but lots of good stuff here
These four are probably the most prominent; but there are others, and excellent work can be found in all of them.
In Theory Only - University of Michigan graduate student journal, no longer published
Indiana Theory Review - from Indiana University
Intégral - from Eastman
Don't forget to ask your friendly reference librarian for help!