“ON-FARM FARMERS’ PARTICIPATORY EVALUATION OF THE IMPACT OF POSITIVE SELECTION ON SEED TUBER YAM ( Dioscorea Rotundata Poir) PRODUCTION FROM TWO SOURCES IN EBONYI SOUTHEASTERN NIGERIA”. Global Journal of Advanced Engineering Technologies and Sciences, vol. 5, no. 8, Aug. 2018, pp. 25-33, https://gjaets.com/index.php/gjaets/article/view/105.