Layman, Richard, ed. Discovering "The Maltese Falcon" and Sam Spade. Rev. ed. San Francisco: Vince Emery Productions, 2005.
Thompson, George J. Hammett's Moral Vision. San Francisco: Vince Emery Productions, 2007.
Layman, Richard. Shadow Man. San Diego: Harcourt Brace Jovanovich Books, 1981.
Black Mask Magazine
This website is a cyber-reincarnation of the popular pulp magazine. Contains history, cover art, and links to some of the fiction that appeared during the heyday of the magazine.
Allan Pinkerton and his Detective Agency
This website gives a good overview of the history of the Pinkerton National Detective Agency.
Museum of the City of San Francisco
A website dedicated to preserving the colorful history of San Francisco.
American Masters: Dashiell Hammett on PBS.org
American Masters website about Dashiell Hammett's life and his writing.