Nowlan, M. O. (1983). Stubborn strength. Academic Press Canada.
Lua i Stíl Chicago (17ú heag.)Nowlan, Michael O. Stubborn Strength. Ontario, Canadá: Academic Press Canada, 1983.
Lua MLA (9ú heag.)Nowlan, Michael O. Stubborn Strength. Academic Press Canada, 1983.
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