Herzschuh, U., Ni, J., Birks, H. J. B., & Böhner, J. (2011). Driving forces of
mid-Holocene vegetation shifts on the upper Tibetan Plateau, with emphasis on changes in atmospheric CO2 concentrations. QUATERNARY SCIENCE REVIEWS, 30, 1907-1917. doi:10.1016/j.quascirev.2011.03.007.