https://chartmasters.org/diana-ross-...d-songs-sales/

This looks new and there are masses of information in here

You can also find Supremes information

I can’t say I’ve studied this closely - I scanned it for 10 or 15 minutes over Christmas

What caught my attention most of all was information indicating many [[or most) of the early Supremes singles selling over a million copies each. Also I remember being surprised by the sales of Everything is Everything