Reichl 2019, p. 20. Reichl, Eugen (2019). The Soviet Space Program: the Lunar Mission Years 1959–1976. Translated by David Johnston. Atglen, Pennsylvania: Schiffer Publishing. ISBN978-0-7643-5675-9. LCCN2017955750.
Reichl 2019, p. 21. Reichl, Eugen (2019). The Soviet Space Program: the Lunar Mission Years 1959–1976. Translated by David Johnston. Atglen, Pennsylvania: Schiffer Publishing. ISBN978-0-7643-5675-9. LCCN2017955750.