“…$$ When (IL2) and (IR2) hold, we find
is an upper solution to () if
such that the initial condition holds (see Appendix ). When the (IL1) and (IR1) is true, we can refer to the asymptotic behavior of traveling waves in delayed equations (see a recent work by Xu & Xiao [
40]) to obtain an upper solution. For other cases, the conclusion can be verified by different combinations of these cases.…”