Peterson, R. (1997). Pigskin: The early years of pro football. Oxford University Press.
Lua i Stíl Chicago (17ú heag.)Peterson, Robert. Pigskin: The Early Years of Pro Football. New York: Oxford University Press, 1997.
Lua MLA (9ú heag.)Peterson, Robert. Pigskin: The Early Years of Pro Football. Oxford University Press, 1997.
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