Helander, C. (2002). Farming system research: An approach to developing of sustainable farming systems and the role of white clover as a component in nitrogen management.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Helander, Carl-Anders. Farming System Research: An Approach to Developing of Sustainable Farming Systems and the Role of White Clover as a Component in Nitrogen Management. 2002.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Helander, Carl-Anders. Farming System Research: An Approach to Developing of Sustainable Farming Systems and the Role of White Clover as a Component in Nitrogen Management. 2002.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.