1. College of Computer Science and Engineering, Shandong University of Science and Technology, Qingdao, Shandong, China
2. Department of Computer Science and Engineering, Ajay Kumar Garg Engineering College, Ghaziabad, India
3. Department of Mathematics, Chaudhary Charan Singh University, Meerut, India
4. Federal University of Piauí, 64049-550 Teresina, PI, Brazil
5. Instituto de Telecomunicações, Lisboa 1049-001, Portugal