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- [1] ON THE EXISTENCE OF PERIODIC-SOLUTIONS TO LIENARD EQUATIONS IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII MATEMATIKA, 1989, (10): : 27 - 29
- [4] ON THE EXISTENCE OF PERIODIC-SOLUTIONS FOR THE GENERALIZED LIENARD EQUATION BOLLETTINO DELLA UNIONE MATEMATICA ITALIANA, 1989, 3B (01): : 155 - 168
- [8] EXISTENCE OF SOME PERIODIC-SOLUTIONS IN LIENARD-TYPE EQUATIONS IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII MATEMATIKA, 1987, (03): : 3 - 5