Infinitely Many Periodic Solutions for the Equation: u tt - u xx ± | u | p-1 u = f(x, t). II
Kazunaga Tanaka · Transactions of the American Mathematical Society · 1988
Kazunaga Tanaka, Infinitely Many Periodic Solutions for the Equation: $u_{tt} - u_{xx} \pm |u|^{p-1}u = f(x, t)$. II, Transactions of the American Mathematical Society, Vol. 307, No. 2 (Jun., 1988), pp. 615-645