Zhang Fang, Li Wei, Zhang Yao-Yu, Xue Xi-Chang, Jia Li-Qun. Conformal invariance and conserved quantity of Mei symmetry for Appell equations in nonholonomic systems of Chetaev’s type with variable massJ. Acta Physica Sinica, 2014, 63(16): 164501. DOI: 10.7498/aps.63.164501