A. Biswas - Natl Res Nucl Univ, Dept Appl Math, 31 Kashirskoe Hwy, Moscow 115409, Russia
A. Dakova - Univ Plovdiv Paisii Hilendarski, Phys & Technol Fac, 24 Tsar Asen Str, Plovdiv 4000, Bulgaria
S. Khan - Alabama Agricultural and Mechanical University
M. Ekici - Yozgat Bozok Univ, Fac Sci & Arts, Dept Math, TR-66100 Yozgat, Turkey
L. Moraru - "Dunarea de Jos" University of Galati
M. R. Belic - Inst Phys Belgrade, Pregrevica 118, Zemun 11080, Serbia
Physics and Technology Faculty, University of Plovdiv “Paisii Hilendarski”, 24 Tsar Asen Str., 4000 Plovdiv, Bulgaria