The following websites are very helpfull tools in the trading community.
 

• Encora.it - Database of existing musical recordings.

• Sassy Guide - Very helpfull website with all the info you need to know when starting out in the trading community.

• Master Releases Carrd - Website that lists the formats en filesizes from popular master releases. Very helpfull when deciding if you have the original files, or a rip. 

• Completionism Carrd - Website that list collector's that have big collection's of certain shows. Very helpfull when trying to collect recordings from a specific show.