Affiliation: | aDepartment of Mathematics, Sichuan Normal University, Chengdu, Sichuan 610066, PR China;bDepartment of Mathematics, Sichuan University, Chengdu, Sichuan 610064, PR China;cState Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu, 610500, PR China;dDepartment of Applied Mathematics, Southwest Petroleum University, Chengdu, 610500, PR China |