Duyet H N, Thuan T T and Son N D 2010: Effects on sow reproduction and piglet performance of replacing soybean meal by a mixture of sweet potato leaves, water spinach and fresh cassava foliage in the diets of Mong Cai and Yorkshire sows. Livestock Research for Rural Development. Volume 22, Article #59. Retrieved , from http://www.lrrd.org/lrrd22/3/duye22059.htm