@INPROCEEDINGS {NG: 1994a, title = {Production and distribution of virus-free yam (Dioscorea rotundata Poir.)}, author = {Ng, S. Y. C. }, editor = {Ofori, F and Hahn, S. K. }, booktitle = {Tropical root crops in a developing economy: proceedings of the 9th Symposium of the International Society for Tropical Rooy Crops, 20-26 October 1991, Accra, Ghana}, year = {1994}, pages = {324--328}, publisher = {ISTRC; Government of Ghana; International Institute of Tropical Agriculture (IITA)}, address = {Accra, Ghana}, note = {RTB; Root and Tuber; Yam}, }