Peter, Lev (2006-11-06). Transforming the screen, 1950-1959. History of the American cinema. 7. University of California Press. p. 177. ISBN0-520-24966-6. https://books.google.com/books?id=TEGl2Ele_XoC&pg=PA177. "Invasion films were common in the 1950s featuring a variety of aliens portrayed as superior to earthlings both in intelligence and technology. In these films, aliens represent what some Americans feared about the Soviets. Invaders, friends or enemies, and often with the help of robots, either come to warn earthlings or destroy them with superior technology. Sometimes, the invaders use the strategy of infiltration, taking over the minds of the people, making slaves of them or appropriating their bodies, thus making war unnecessary. In some instances, the aliens already had a similar appearance - in Star Trek, while officially made contact with Humanity in 2063, (and were not "invaders" - some were shipwreck survivors, others time-travelers, accompanied by at least one Human, from a future where their respective worlds were allies) no fewer than six Vulcans had spent some time on Earth, passing as Human simply by using hair or skullcaps to conceal their pointed ears."
