Harmon, D. E. (2018). The early days of space exploration. Britannica Educational Publishing in association with Rosen Educational Services.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रHarmon, Daniel E. The Early Days of Space Exploration. New York, NY: Britannica Educational Publishing in association with Rosen Educational Services, 2018.
एमएलए (8वां संस्करण) प्रशस्ति पत्रHarmon, Daniel E. The Early Days of Space Exploration. Britannica Educational Publishing in association with Rosen Educational Services, 2018.
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