John Dexter
Pseudonym of Marion Zimmer Bradley
A house name owned by Nightstand Books and used by many writers to produce soft porn/sleaze novels in the 1960s. As per <a href="http://bookscans.com/Oddities/johndexter.htm">bookscans.com</a>, the list of SF authors who are known to have written as "John Dexter" includes Marion Zimmer Bradley, Zach Hughes, Robert Silverberg, and George H. Smith. Other authors of genre interest include Lawrence Block, Arthur Jean Cox, Richard Curtis, Donald E. Westlake, and Harry Whittington among others.