Sorry for the late reply (I thought there were no responses), and thanks so much for your responses. One question though. Where could one find 1. information about old ipc classes being replaced with new ones in Patstat 2011, and 2. the definitions of the 4-digit IPC classes. The IPC class informati...

Hi all I am interested in extracting "unique" 4-digit(first four) ipc codes from a certain set of docdb families. I see that there are different versions of ipc (starting 2006) in my version of patstat (sep2009). What I wonder is if I keep unique IPCs in each family based on the entire set...