Knutson, R. D., Penn, J. B., & Flinchbaugh, B. L. (1998). Agricultural and food policy (4th ed.). Prentice Hall.
Lua i Stíl Chicago (17ú heag.)Knutson, Ronald D., J. B. Penn, agus Barry L. Flinchbaugh. Agricultural and Food Policy. 4th ed. Upper Saddle River, N.J: Prentice Hall, 1998.
Lua MLA (9ú heag.)Knutson, Ronald D., et al. Agricultural and Food Policy. 4th ed. Prentice Hall, 1998.
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