Downregulation of Caffeic Acid 3-<i>O</i>-Methyltransferase and Caffeoyl CoA 3-<i>O</i>-Methyltransferase in Transgenic Alfalfa: Impacts on Lignin Structure and Implications for the Biosynthesis of G and S LigninDianjing Guo, Richard A. Dixon|The Plant Cell|2001Cited by 517