University of Illinois (Urbana-Champaign campus). Elementary-School Science Project & University of Illinois (Urbana-Champaign campus). Elementary-School Science Project. (1962). Astronomy (Rev. ed.). University of Illinois, Elementary School Science Project.
Chicago-referens (17:e uppl.)University of Illinois (Urbana-Champaign campus). Elementary-School Science Project och University of Illinois (Urbana-Champaign campus). Elementary-School Science Project. Astronomy. Rev. ed. Urbana, Ill.: University of Illinois, Elementary School Science Project, 1962.
MLA-referens (8:e uppl.)University of Illinois (Urbana-Champaign campus). Elementary-School Science Project och University of Illinois (Urbana-Champaign campus). Elementary-School Science Project. Astronomy. Rev. ed. University of Illinois, Elementary School Science Project, 1962.