S. Ketema, “Tef (Eragrostsis tef) Series: Promoting the Conservation and Use of Underutilized and Neglected Crops,” Institute of Plant Genetics and Crop Plant Research, Getersleben/International Plant Genetic Resources Institute, Rome, 1997.
 A. Woldeab, T. Mamo, M. Bekele and T. Alema, “Soil Fertility Management Studies on Wheat in Ethiopia. In: H. Gebre Mariam, D. G. Tanner and M. Huluka, Eds., Wheat Research in Ethiopia: A Historical Perspective, IAR/ CIMMYT, Addis Ababa, 1991, pp. 137-172.
 T. Mamo and I. Haque, “Phosphorus Status of Some Ethiopian Soils. II. Forms and Distribution of Inorganic Phosphorus and Their Relation to Available Phosphorus,” Trop.Agric. (Trinidad), Vol. 68, No. 1, 1991, pp. 2-8.
 L. Ozturk, S. Eker, B. Torun and I. Cakmak, “Variation in Phosphorus Efficiency among 73 Bread and Durum Wheat Genotypes Grown in a Phosphorus-Deficient calcareous Soil,” Plant Soil, Vol. 269, No. 1-2, 2005, pp. 69-80. http://dx.doi.org/10.1007/s11104-004-0469-z
 B. Sattelmacher, W. J. Horst and H. C. Becker, “Factors That Contribute to Genetic Variation for Nutrient Efficiency of Crop Plants,” Journal of Plant Nutrition and Soil Science, Vol. 157, No. 3, 1994, pp. 215-224.
 D. Föhse, N. Claassen and A. Jungk, “Phosphorus Efficiency of Plants. I: External and Internal P Requirement and P Uptake Efficiency of Different Plant Species,” Plant Soil, Vol. 110, No. 1, 1998, pp. 101-109.
 J. P. Lynch and K. M. Brown, “Topsoil Foraging—An Architectural Adaptation of Plants to Low Phosphorus Availability,” Plant Soil, Vol. 237, No. 2, 2001, pp. 225-237. http://dx.doi.org/10.1023/A:1013324727040
 T. S. Gahoonia and N. E. Nielsen, “Barley Genotypes with Long Root Hairs Sustain High Grain Yields in Low-P Field,” Plant Soil, Vol. 262, No. 1-2, 2004, pp. 55-62.
 S. J. Yun and S. M. Kaeppler, “Induction of Maize Acid Phosphatase Activities under Phosphorus Starvation,” Plant Soil, Vol. 237, No. 1, 2001, pp. 109-115.
 J. Wasaki, T. Yamamura, T. Shinano and M. Osaki, “Secreted Acid Phosphatase Is Expressed in Cluster Roots of Lupin in Response to Phosphorus Deficiency,” Plant Soil, Vol. 248, No. 1-2, 2003, pp. 129-136.
 J. R. Caradus and R. W. Snaydon, “Aspects of Phosphorus Nutrition of White Clover Populations. I: Inorganic Phosphorus Content of Leaf Tissue,” Journal of Plant Nutrition, Vol. 10, No. 3, 1987, pp. 273-285.
 T. S. Gahoonia, N. E. Nielsen and O. B. Lyshede, “Phosphorus (P) Acquisition of Cereal Cultivars in the Field at Three Levels of P Fertilization,” Plant Soil, Vol. 211, No. 2, 1999, pp. 269-281.
 L. D. Osborne and Z. Rengel, “Screening Cereals for Genotypic Variation in Efficiency of Phosphorus Uptake and Utilization,” Australian Journal of Agricultural Research, Vol. 53, No. 3, 2002, pp. 295-303.
 N. K. Fageria and V. C. Baligar, “Upland Rice Genotypes Evaluation for Phosphorus Use Efficiency,” Journal of Plant Nutrition, Vol. 20, No. 4-5, 1997, pp. 499-509.
 J. M. Bremner, “Total Nitrogen,” In: C. A. Black, D. D. Evants, L. E. Ensminger, J. L.White, F. E. Clark and R. C. Dinaeur, Eds., Methods of Soil Analysis, American Society of Agronomy, Madison, 1965, pp. 1149-1178.
 A. Deressa, W. Negassa, F. Getaneh and B. Dinsa, “Response of tef to Nitrogen and Phosphorus Fertilizers under Farmers’ Conditions,” In: A. Zeleke, H. Tefera, G. Keneni, A. Ayana, T. Tefera, S. Assefa, D. Debelo and B. Simane, Eds., Sebil: Proceedings of the 11th Conference of the Crop Science Society of Ethiopia, Addis Ababa, 2004, pp. 176-181.
 K. N. Devi, L. N. K. Singh, T. S. Devi, H. N. Devi, T. B. Singh, K. K. Singh and W. M. Singh, “Response of Soybean [Glycine max (L.) Merrill] to Sources and Levels of Phosphorus,” Journal of Agricultural Science, Vol. 4, No. 6, 2012, pp. 44-53.
 A. Gunes, A. Inal, M. Alpaslan and I. Cakmak, “Genotypic Variation in Phosphorus Efficiency between Wheat Cultivars Grown under Greenhouse and Field Conditions,” Soil Science and Plant Nutrition, Vol. 52, No. 4, 2006, pp. 470-478.
 A. Akram, M. Fatima, S. Ali, G. Jilani and R. Asghar, “Growth, Yield and Nutrients Uptake of Sorghum in Response to Integrated Phosphorus and Potassium Management,” Pakistan Journal of Botany, Vol. 39, No. 4, 2007, pp. 1083-1087.
 E. A. Akinrinde and T. Gaizer, “Differences in the Performance and Phosphorus-Use Efficiency of Some Tropical Rice (Oryza sativa L.) Varieties,” Pakistan Journal of Nutrition, Vol. 5, No. 3, 2006, pp. 206-211.
 T. Mamo, C. Richter and A. Hoppenstedt, “Phosphorus Response Studies on Some Varieties of Durum Wheat (Triticum durum Desf.) and tef (Eragrostis tef (Zucc) (Trotter) Grown in Sand Culture,” Journal of Agronomy and Crop Science, Vol. 176, No. 3, 1996, pp. 189-197.
 R. C. Menary and J. van Staden, “Effects of Phosphorus Nutrient and Cytokinins on Flowering in the Tomato (Lycopersicon esculentum Mill),” Australian Journal of Plant Physiology, Vol. 3, No. 2, 1976, pp. 201-205.
 M. S. Rahman and J. H. Wilson, “Effect of Phosphorus Applied as Superphosphate on Rate of Development and Spikelet Number per Ear in Different Cultivars of Wheat,” Australian Journal of Agricultural Research, Vol. 28, No. 2, 1977, pp. 183-186.
 J. M. Horgan and P. F. Wareing, “Cytokinins and the Growth Response of Seedlings of Betula pendula Roth. and Ancer pseudoplantanus L. to Nitrogen and Phosphorus Deficiencies,” Journal of Experimental Botany, Vol. 31, No. 121, 1980, pp. 525-532.
 M. A. Hussaini, V. B. Ogunlela, A. A. Ramalan and A. M. Falaki, “Mineral Composition of Dry Season Maize (Zea mays L.) in Response to Varying Levels of Nitrogen, Phosphorus and Irrigation at Kadawa, Nigeria,” World Journal of Agricultural Sciences, Vol. 4, No. 6, 2008, pp. 775-780.