Columbia subject headings:
Astronautics--Soviet Union.
Gagarin, Yuri Alekseyevich, 1934-1968.
Titov, G. S. (German Stepanovich), 1935-2000.
Harvard subject headings:
Astronautics--Soviet Union
Gagarin, Yuri Alekseyevich, 1934-1968
Titov, G. S. (German Stepanovich), 1935-
Princeton subject headings: