PS--when I worked at the Yearbook of Experts, Authorities and Spokespersons
(or as I called it, the Yearbook of Perverts, Wannabees and Salespersons),
we would sometimes be asked how we knew the people in our book were really
experts. "Easy," we'd reply, "their payments cleared!" Or as the publisher
liked to say, "Anyone with the cover charge is welcome to our party." He
liked bar analogies. 

DW