1. Non-negative solutions of linear parabolic equations;Aronson;Ann. Scuola Norm. Sup. Pisa Cl. Sci. (4),1968
2. Asymptotic Methods in the Theory of Nonlinear Oscillations;Bogoliubov,1961
3. Parabolic Systems;Eidelman,1969
4. Partial Differential Equations of Parabolic Type;Friedman,1967
5. Theory of Stochastic Processes;Gihman,1979