Dmitriy V Dolgy Author

Leonid Aschepkov is a professor in the Department of Mathematical Methods of Economy at Far Eastern Federal University.
Dmitriy V. Dolgy is a professor at the Institute of Natural Sciences at Far Eastern Federal University in Vladivolstok, Russia and at Hanrimwon, Kwangwoon University in Seoul, Republic of Korea.
Taekyun Kim is a professor in the Department of Mathematics at the College of Natural Science at Kwangwoon University. 

Ravi P. Agarwal is a professor and the chair of the Department of Mathematics at Texas A&M University.