1. Institute of Industrial Ecology UB RAS Ural Federal University Yekaterinburg 620990 Russia
2. Department of Mathematics, College of Sciences King Saud University P. O. Box 2455, Riyadh 11451 Saudi Arabia
3. College of Mathematics and Systems Science Shandong University of Science and Technology Qingdao 266590 China
4. Section of Mathematics, Department of Civil Engineering Democritus University of Thrace Xanthi Greece
5. Data Recovery Key Laboratory of Sichuan Province Neijiang Normal University Dongtong Road 705, Neijiang 641100 China
6. General Department, Euripus Campus National and Kapodistrian University of Athens GR-34400 Greece