Vande Vere, E. K. (1979). Rugged heart: The story of George I. Butler. Southern Publishing Association.
Lua i Stíl Chicago (17ú heag.)Vande Vere, Emmett K. Rugged Heart: The Story of George I. Butler. Nashville, TN: Southern Publishing Association, 1979.
Lua MLA (9ú heag.)Vande Vere, Emmett K. Rugged Heart: The Story of George I. Butler. Southern Publishing Association, 1979.
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