... 1997.3 A. Cabada and L. Sanchez, A positive operator approach to the Neumann problem for a secondorder ordinary differential equation,” Journal of Mathematical Analysis and Applications, vol. ... compression and expansion of cones, and obtained the existence of at least two positive solutions under reasonable conditions. In 6, the authorsestablished the existence of sign-changing solutions and ... 360–364, 2000.6 F. Li, Y. Zhang, and Y. Li, “Sign-changing solutions on a kind of fourth-order Neumann boundaryvalue problem,” Journal of Mathematical Analysis and Applications, vol. 344, no. 1,...