A Note on Monotone Iteration Method for Traveling Waves of Reaction-Diffusion Systems with Time Delay

For a monotone reaction-diffusion system with or without time delay, a standard approach to show the existence of a mono-stable traveling wave solution is the monotone iteration that requires the construction of a pair of upper and lower solution. In this note we will show that the monotone iteration approach can be improved by just constructing an upper solution. This improvement gives more freedom for the construction of an upper solution.