Griffin, S., Treffeisen, P. A., & Heady, E. O. (1978). Iowa's commercial farms: An analysis of the USDA cost of production survey. Center for Agricultural and Rural Development, Iowa State University.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Griffin, Steven, P. Alan Treffeisen, و Earl O. Heady. Iowa's Commercial Farms: An Analysis of the USDA Cost of Production Survey. Ames, Iowa: Center for Agricultural and Rural Development, Iowa State University, 1978.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Griffin, Steven, et al. Iowa's Commercial Farms: An Analysis of the USDA Cost of Production Survey. Center for Agricultural and Rural Development, Iowa State University, 1978.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.