“…The problem of traveling wave solutions has been widely investigated for reaction-diffusion equations ( [3,4,8,9,11,12] and [17]) and integral equations [13,14]. The concept of asymptotic speed of propagation was introduced by Aronson and Weinberger [1,15] for reaction-diffusion equations and applied by Aronson [2], Diekeman [5], Thieme [13], Thieme and Zhao [14], Radcliffe and Rass [10] to integrodifferential and integral equations, and by Weng, Huang and Wu [16] to a lattice differential equation. The extensive references could be found in Thieme and Zhao [14].…”