Williams, J. F. (1956). The principles of physical education (6ª ed.). W:B: Saunders.
Lua i Stíl Chicago (17ú heag.)Williams, Jesse Feiring. The Principles of Physical Education. 6ª ed. Philadelphia: W:B: Saunders, 1956.
Lua MLA (9ú heag.)Williams, Jesse Feiring. The Principles of Physical Education. 6ª ed. W:B: Saunders, 1956.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.