Johnson, E. S. (1956). Theory and practice of the social studies. Macmillan.
Lua i Stíl Chicago (17ú heag.)Johnson, Earl Shepard. Theory and Practice of the Social Studies. New York: Macmillan, 1956.
Lua MLA (8ú heag.)Johnson, Earl Shepard. Theory and Practice of the Social Studies. Macmillan, 1956.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.