Here is a list of Operation Doubles' articles hosted at Tennis4you:
Article #001 - Eyework at the Net in Doubles
Article #002 - Footwork at the Net in Doubles
Article #003 - Being in the Right Place at the Right Time
Article #004 - Getting Out of Harm's Way
Article #005 - Balance and the Overhead Smash
Article #006 - Understanding Tennis Doubles Strategy
Article #007 - Switching in Tennis Doubles
Article #008 - The Switch Trick Play