These are the 6 articles I wrote for the ACBL Bulletin on Doubles (in order of difficulty):
Takeout Doubles
Negative Doubles
Responsive Doubles
Support Doubles
Low Level Doubles
Lead-directing, Maximal and other Doubles
You might also consider getting Larry's book on Doubles and Redoubles HERE or try Michael's Doubles Webinar which you can find HERE.
or 1
opening bid as forcing (or semi-forcing) fo