J. Henderson et Hb. Thompson, Multiple symmetric positive solutions for a second order boundary value problem, P AM MATH S, 128(8), 2000, pp. 2373-2379
For the second order boundary value problem, y" + f(y) = 0, 0 less than or
equal to t less than or equal to 1, y(0) = 0 = y(1), where f : R --> [0, in
finity); growth conditions are imposed on f which yield the existence of at
least three symmetric positive solutions.