Van An L, Hong TTT, Ogle B, Lindberg JE. Utilization of Ensiled Sweet Potato (Ipomoea batatas (L.) Lam.) Leaves as a Protein Supplement in Diets for Growing Pigs. Tropical Animal Health and Production. 2005 Jan;37(1):77–88. doi: 10.1023/b:trop.0000047937.41355.4d.