1. Research Scholar, Dept. of Mathematics, Institute of Science, Banaras Hindu Univ., Varanasi 221005, India.
2. Distinguished Professor, Regents Professor, and Caroline & William N. Lehrer Distinguished Chair in Water Engineering, Dept. of Biological Engineering and Agricultural Engineering, and Zachry Dept. of Civil Engineering, Texas A&M Univ., 321 Scoates Hall, 2117 TAMU, College Station, TX 77843-2117 (corresponding author).
3. Professor, Dept. of Mathematics, Institute of Science, Banaras Hindu Univ., Varanasi 221005, India.