“…where a < t 1 < t 2 < t 3 < b and y 1 , y 2 , y 3 ∈ R. Third-order ordinary differential equations arise as models for certain natural phenomena such as boundary-layer flow in fluid mechanics involving convection in a porous medium, or a flow along a standing wall or stretched sheet (see [1,4,6,16,[47][48][49]51,52]). Other theoretical works have dealt with third-order equations devoted to, for example, upper and lower solutions, periodic solutions, limit-point and limit-circle criteria and singular boundary-value problems (see [2,3,5,32,36,41,45,50]).…”