StenbergK, Galbe M, Zacchi G. The influence of lactic acid formation on the stimultaneous saccharifacation and fermantation of softwood to ethanol-using saccharomyces cerevisiae and beta-glucosidase and cellulase-mediated hydrolysis [J]. Enzyme and Microbial Technology, 1990(1):71-79.doi:10.1016/S0141-0229(99)00127-1.