* The 0-T human tester squad was probably based on the [[http://ru.wikipedia.org/wiki/%D0%9F%D0%B5%D1%80%D0%B2%D1%8B%D0%B9_%D0%BE%D1%82%D1%80%D1%8F%D0%B4_%D0%BA%D0%BE%D1%81%D0%BC%D0%BE%D0%BD%D0%B0%D0%B2%D1%82%D0%BE%D0%B2_%D0%A1%D0%A1%D0%A1%D0%A0 First Soviet Space Squad]]--originally twelve (later, twenty) elite pilots hand-picked from the entire Red Air Force for the Soviet space program in 1960 (three years before the novel was written). Their US equivalent would be the [[http://en.wikipedia.org/wiki/Mercury_Seven Mercury Seven]].
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