By courtesy of:
George A. Olah
Science 1970, 168, 1298
See also:
Superacids
George A. Olah; G. K. Surya Prakash; Jean Sommer
Science 1979, 206, 13
and recently:
Superacids: It’s a Lot about Anions
Darryl D. DesMarteau
Science 2000, 289, 72