Structural changes of lignins in natural Populus variants during different pretreatments Authors Yang, Haitao; Yoo, Chang Geun; Meng, Xianzhi; Pu, Yunqiao; Muchero, Wellington; Tuskan, Gerald A.; Tschaplinski, Timothy J.; Ragauskas, Arthur J.; and Yao, La n Journal-Book Bioresource Technology Year 2020