[ccp4bb] The number of protein-protein complex in recent years

[Wei Feng]

 Dear all,
I want to do a statistics about the number of protein-protein complexes 
deposited in PDB in recent years.(1972~1992,1993...2012)
I tried keywords "protein-protein complex", "protein complex" etc. in the 
search of PDB but all of them are fail.
Can everyone tell me how to do?
Thank you very much!
Wei