1. Ames, W.F.: Numerical Methods for Partial Differential Equations. Academic Press, San Diego, 1992
2. Berman, A., Plemmons, R.: Nonnegative Matrix in the Mathematical Science. Academic Press, New York, 1979
3. Cushing, J.M.: Integrodifferential Equations and Delay Models in Population Dynamics. In: Lecture Notes in Biomathematics, Vol. 20, Springer-Verlag, New York, 1977
4. Feng, W., Lu, X.: Harmless delays for permanence in a class of population models with diffusion effect. J. Math. Anal. Appl. 206, 547–566 (1997)
5. Forsythe, G.E., Wasow, W.R.: Finite Difference Methods for Partial Differential Equations. John Wiley, New York, 1964