I've been looking around in the daytime with a flashlight for their early albums and first works. They are difficult to find, but when I do, it's a treasure trove of funk grooves, awesome chords, deep basslines and serious vocal power.
So far, I have (and have transferred to CD/MP3) :
He Gave Me Nothing To Lose (1979) Is My Living In Vain (1980) You Brought The Sunshine (1981) Sincerely (1982)