Fritz Lang expert David Kalat, in his authoritative book "The Strange Case of Dr. Mabuse", regards "Scream and Scream Again" (1969), "Dorian Gray im Spiegel der Boulevardpresse" (1984) and "Docteur M." (1990) as ancillary extentions of Lang's "Dr. Mabuse" series. In Kalat's view, "Docteur M." (1990) is an unofficial series entry.