Department of Physics University of Agriculture P.M.B.2240 Abeokuta Nigeria;
Department of Physics Lancaster University Lancaster LA1 4YB United Kingdom;
Institut für Theoretische Physik Technische Universit(a)t Clausthal Arnold-Sommerfeld Str.6 38678 Clausthal-Zellerfeld Germany;
Department of Physics Olabisi Onabanjo University A;