[NTG-context] bibmod question

Hi I'm using the bibmod module with the 'ams' style (bibl-ams.tex). If I have two (or more) references by the same author, from the same year, in my bibtex database. The years are printed in the reference list as eg. 2000a, 2000b, etc., even if I only quote one of the. Since the 'ams' style is citing by number, there is no use for these additional letters. Is there a way to turn those off? Thanks, Peter