why do contacts keep duplicating in my address book?

why do contacts keep duplicating in my address book?

i started to download maverick, paused, then finished, decided i didn't want it and deleted it from applications.

meanwhile my address book listings within each group are duplicating, the names are being deleted, and i am left with a list of some emails and some names within each group. i have tried to correct them one by one but they revert to the email or duplicate.