USDA & Economic research service. (2001). Agri-environment polisy at the crossroads: Guideposts on a changing landscape; agricultural economic report No794.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)USDA و Economic research service. Agri-environment Polisy at the Crossroads: Guideposts on a Changing Landscape; Agricultural Economic Report No794. 2001.
توثيق جمعية اللغة المعاصرة MLA (الإصدار التاسع)USDA و Economic research service. Agri-environment Polisy at the Crossroads: Guideposts on a Changing Landscape; Agricultural Economic Report No794. 2001.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.