“…Existence and nonexistence of travelling waves in those models have been recently studied in Chow [4], Chow et al [5], and Zinner [6] mostly with the cubic (or bistable, double-well) nonlinearities of the form ( ) = ( − )(1 − ), with > 0 and ∈ (0, 1) (this special case of FKPP equation is being referred to as Nagumo equation). In contrast, various reaction functions have been proposed in models without spatial interaction, for example, Xu et al [7]. Motivated by these facts, we allow for a general form of the reaction function in this paper (i.e., we do not restrict ourselves to cubic nonlinearities).…”