Biftu، K. N.، و Qasem، J. R. S. (2002). Some Physiological Aspects of the Competitive Ability of Cowpea "Vigna Sinensis L." and Red Root Pigweed "Amaranthus Retroflexus L." with Special Reference to Moisture and Phoshorus Fertilizer (رسالة ماجستير غير منشورة). الجامعة الاردنية، عمان. مسترجع من http://search.mandumah.com/Record/550723
Biftu، Kedir Nefo، و Jamal Ragheb Said Qasem. "Some Physiological Aspects of the Competitive Ability of Cowpea "Vigna Sinensis L." and Red Root Pigweed "Amaranthus Retroflexus L." With Special Reference to Moisture and Phoshorus Fertilizer" رسالة ماجستير. الجامعة الاردنية، عمان، 2002. مسترجع من http://search.mandumah.com/Record/550723