Star Trek: "The Enemy Within"

From Author Wars - https://authorwars.com/books/star-trek-the-enemy-within-1290932.html

Overview:

Title: Star Trek: "The Enemy Within"
Author: Richard Matheson
Year: 1966
Type: Short Fiction

Editions/Publications:

Unknown. Matheson Uncollected: Volume One (Unknown, Richard Matheson, Gauntlet Publications, ISBN-10: 9781887368971, 266 pages, Hardcover, Collection)