periodic solution; nonlinear second-order differential equation with a parameter; Schauder fixed point theorem
This paper establishes effective sufficient conditions for existence and uniqueness of periodic solutions of a one-parameter differential equation $u''-q(t)y=f(t,y,y',\mu)$ vanishing at an arbitrary but fixed point.
 S. Staněk: Three-point boundary value problem of nonlinear second order differential equation with parameter
. Czechoslovak Math. J. 42(117) (1992), 241-256. MR 1179496