1. Ladde GS, Lakshmikantham V, Zhang BG.Oscillation theory of differential equations with deviating arguments. New York: Marcel Dekker, 1987
2. Bykov Ya Y, Kultaev T ch. Oscillation of solutions of a class of parabolic equations.Izv Akad Nauk Kirgiz, SSR, 19836: 3–9 (Russian)
3. Georgiou D, Kreith K. Functional characteristic initial value problems.J Math Anal Appl, 1985,107: 414–424
4. Yoshida N. Oscillation of nonlinear parabolic equations with functional arguments.Hiroshima Math J. 1986,16: 305–314
5. Mishev DP, Bainov DD. Oscillation properties of the solutions of a class of hyperbolic equations of neutral type.Funkcialaj Ekvacioj, 1986,29:213–218