1. Subfunctions and second order ordinary differential inequalities;Jackson;Advan. Math.,1968
2. Generalized convex functions and second order differential inequalities;Peixoto;Bull. Amer. Math. Soc.,1949
3. On second order differential inequalities;Jackson,1966
4. A note on second order differential inequalities;Schrader,1968
5. On the inequalities y‴ ⩾ G(x, y, y′, y′');Peixoto;An Acad. Brasil. Ci.,1949