DON'T STOP THE PROMOS 
'TIL YOU GET ENOUGH Don't stop 'til you get enough USA Promo EPIC AS644
Don't stop 'til you get enough USA Promo EPIC AS654
It's hard to see....they look so similar BUT...here they are : 2 twins AGAIN. But...what a difference!
I found that the US promotional copies of "Don't stop 'til you get enough'' are 2. First one has the catalogue number AS644 ("Short version" on side A,3'55'' - "Long version" on side B 5'45''), the second is AS654 (Not named version but 5'45'' that means the long version on both sides).
The Short/Long version (AS644) (PICTURES #1,#2 & #3) comes with a plain white sleeve with cbs gold promo stamp on back, while the AS654 (PICTURES #4,#5 & #6) version it's housed in a common CBS disco "Lips" sleeve used by Epic/CBS for several 12''s at the time. 
The "Lips" sleeve have its promo golden stamp on the back too.