1. A. D. Lyashko and M. M. Karchevskii, ?Investigation of nonlinear problems of seepage theory,? in: Proc. of Seminar on Boundary-Value Problems [in Russian], No. 11, Izd. Kazan' Univ. (1974), pp. 64?72.
2. A. D. Lyashko and M. M. Karchevskii, ?On solving some nonlinear problems of seepage theory,? Izv. Vyssh. Uchebn. Zaved., Mat., No. 6, 73?81 (1975).
3. A. D. Lyashko, I. B. Badriev, and M. M. Karchevskii, ?On variational method for equations with discontinuous monotone operators,? Izv. Vyssh. Uchebn. Zaved., Mat., No. 11, 63?69 (1978).
4. M. M. Karchevskii and I. B. Badriev, ?Nonlinear problems of seepage theory,? in: Numerical Methods of Mechanics of Continuous Media [in Russian], Vol. 10, Novosibirsk (1979), pp. 63?78.
5. A. V. Lapin, ?Investigation of some problems of nonlinear seepage theory,? Zh. Vychisl. Mat. Mat. Fiz.,19, No. 3, 689?700 (1979).