1. Friedman, A.: Partial Differential Equations of Parabolic Type, Englewood Cliffs, N.J.: Prentice-Hall, 1964
2. Odum, E.: Fundamentals of Ecology, 2nd ed., Philadelphia: Saunders, 1959
3. Ito, S.: A boundary value problem of partial differential equations of parabolic type, Duke Math. J.24, 299–312 (1957)
4. Pielou, E.: An Introduction to Mathematical Ecology, New York: Wiley-Interscience, 1969
5. Poole, R.: An Introduction to Quantitative Ecology, New York: McGraw-Hill, 1974