Mazda purchased so many rotary engines over a 40 odd year period. If it wasn't for rotary engine Mazda wouldn't have existed.Even Mazda hasn't managed to make rotaries efficient...
They also fitted them to limited range of GS Citroens and the RO 80 by NSU, who later turned into Audi. The original name was Auto Union, which consisted of 4 different brands and that's why Audi have 4 rings on the bonnet. Probably @12th Monkey would know more than me of the history of Audi/Auto Union/DKW