Everything from Building Science Corporation is excellent, but here is another good report on the same problem:
http://www.tamtech.com/PDF/R.A.P.%20...L.%2008.02.pdf
This is a corporate report designed to support sales of a commercial product:
http://www.tamtech.com/rap.htm
Just wanted to show another alternative that looks valid to me, a homeowner in S.Texas. But if there is already a return in the bedroom, I would first look into whether the problem could be solved by a larger duct to that return. With the advice and consent of a pro who understands airflow of course.
Hope this helps -- Pstu