International Symposium on Horticultural Economics in Developing Countries Alemaya, Ethiopia, International Society for Horticultural Science, Verhaegh, A. P., & Jager, A. d. (1991). First International Symposium on Horticultural Economics in Developing Countries: Alemaya, Ethiopia, 16-23 July 1989. International Society for Horticultural Science.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)International Symposium on Horticultural Economics in Developing Countries Alemaya, Ethiopia, International Society for Horticultural Science, A. P. Verhaegh, و Anton de Jager. First International Symposium on Horticultural Economics in Developing Countries: Alemaya, Ethiopia, 16-23 July 1989. [Wageningen, Netherlands: International Society for Horticultural Science, 1991.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)International Symposium on Horticultural Economics in Developing Countries Alemaya, Ethiopia, et al. First International Symposium on Horticultural Economics in Developing Countries: Alemaya, Ethiopia, 16-23 July 1989. International Society for Horticultural Science, 1991.