On periodic solutions of certain second order ordinary differential equations with periodic coefficients
1964 ◽
Vol 12
(1-2)
◽
pp. 11-16
◽
1977 ◽
Vol 61
(3)
◽
pp. 620-632
◽
1997 ◽
Vol 49
(8)
◽
pp. 1279-1285
◽
1979 ◽
Vol 10
(5)
◽
pp. 985-1001
◽
1974 ◽
Vol 16
(1)
◽
pp. 186-199
◽
1971 ◽
Vol 21
(3)
◽
pp. 491-494
◽
Keyword(s):