The Thirteenth Floor

The science fiction novel "Simulacron-3" was also published under the title "Counterfeit World," and was first published in 1964 by Daniel F. Galouye in the United States, making it one of the first literary descriptions of 'virtual reality.'

When Douglas asks Grierson (Hanlon Fuller) about having flashbacks, Grierson references being in World War I. Since the program is set in the 1930s, prior to the second World War, Grierson wouldn't refer to the previous war as World War I. Before World War II, World War I had other names, most famously "The Great War." While it is a computer program, and knowledge doesn't necessarily operate the same way as in the "real world," there's no logical reason for characters to be programmed with that term, and Hanlon, as the designer, would know the proper terminology for the time since he actually lived during the 1930s.

Before the opening credits, this René Descartes quote is seen on screen: "I think, therefore I am".