By: Joshua Glenn
Meneer [Mister] X (c. 1928), by Valentine Williams.
Mr. X contra Scotland Yard (1949), by Martin Porlock.
De Afschuwelijke X (c. 1946), by R. Poupon.
Christopher Lee’s ‘X’ Certificate (1975)
Organization X (1954), by Hermann Hilgendorff.
Mr. X: King of the Underworld (1942), by Jack Lester.
The “X” People
Let X Be Excitement (1969), by Christie Harris.
Dangerous Mr. X (1929), by Francis Duncan.
A collector’s guide!