The Cowsills In Books

The "Beach Boys": the definitive diary of America's greatest band: on stage and in the studio
by Keith Badman
Backbeat Books October 2004

on Page 132:
May 1966
Friday 10th
Yankee Stadium Bronx, New York, NY Sound Blast '66 show, with Ray Charles (headliner), The Byrds, Stevie Wonder, Jerry Butler, The McCoys, The Marvelettes, The Gentrys, Cowsills, Guess Who. A less—than-sell-out crowd for this big event totals 9,000.