Yang Xin-Fang, Sun Xian-Ting, Wang Xiao-Xiao, Zhang Mei-Ling, Jia Li-Qun. Mei symmetry and Mei conserved quantity of Appell equations for nonholonomic systems of Chetaevs type with variable massJ. Acta Physica Sinica, 2011, 60(11): 111101. DOI: 10.7498/aps.60.111101