Du Bois, W. E. B. (William Edward Burghardt). The Soviet space flights. 1961. Web. 27 Feb 2021. <https://www.digitalcommonwealth.org/search/commonwealth-oai:9s165f72m>.

Du Bois, W. E. B. (William Edward Burghardt). (1961). The Soviet space flights [Manuscript]. Retrieved from https://www.digitalcommonwealth.org/search/commonwealth-oai:9s165f72m

Du Bois, W. E. B. (William Edward Burghardt). "The Soviet space flights." Manuscript. 1961. Digital Commonwealth, https://www.digitalcommonwealth.org/search/commonwealth-oai:9s165f72m (accessed February 27, 2021).