The Rocky Mountain Journal of Mathematics
Cone theory is applied to a class of two-point boundary value problems for ordinary differential equations. Criteria for the existence of extremal points are obtained. These criteria are in terms of the existence of nontrivial solutions that lie in a cone, and in terms of the spectral radius of an associated compact linear operator.
Eloe, Paul W.; Hankerson, Darrel; and Henderson, Johnny, "Positive solutions and J-focal points for two-point boundary value problems" (1992). Mathematics Faculty Publications. 120.