De-Ping Shi

College of Mathematics, Inner Mongolia University for Nationalities, Tongliao City, China

Bo-Yan Xi

College of Mathematics, Inner Mongolia University for Nationalities, Tongliao City, China

Feng Qi

College of Mathematics, Inner Mongolia University for Nationalities, Tongliao City, China
Department of Mathematics, College of Science, Tianjin Polytechnic University, Tianjin City, China;Institute of Mathematics, Henan Polytechnic University, Jiaozuo City, Henan Province, China