As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT#2265, BOS-RSW. '(AIRCRAFT DECLARED AN EMERGENCY AND PERFORMED AN AIR TURN BACK TO BOS). 'DIRTY SOCKS/ GYM BAG SMELL STARTED AT 500' ON TAKEOFF. REMAINED PERSISTENT. DIDN'T DISSIPATE AT ALL UNTIL FUMES REMOVAL PROCEDURE, THEN DISSIPATED VERY SLOWLY. IN COCKPIT CABIN WORSE IN AFT.' (SUPPLEMENTAL INFORMATION TO FOLLOW)