[2] Andres, J., Malaguti, L., Taddei, V.: 
A bounding function approach to multivalued boundary values problems. Set-valued Methods in Dynamic Systems, Special Issue of Dynam. Systems Appl. 16 (2007), 37–48. 
MR 2305427 
[4] Erbe, L., Schmitt, K.: 
Boundary value problems for second order differential equations. Nonlinear Anal. Appl., Proc. 7th Int. Conf. (Arlington 1986), Lect. Notes Pure Appl. Math. 109 (1987), 179–184. 
MR 0912292 | 
Zbl 0636.34012 
[5] Gaines, R .E., Mawhin, J.: 
Coincidence degree and nonlinear differential equations. Lectures Notes in Math., Springer–Verlag, Berlin 586 (1977). 
MR 0637067 | 
Zbl 0339.47031 
[6] Hartman, P.: 
Ordinary Differential Equations. Wiley-Interscience, New York, 1969. 
MR 0419901 
[9] Mawhin, J.: 
The Bernstein-Nagumo problem and two-point boundary value problem for ordinary differential equations, Qualitative theory of differential equations. Colloq. Math. Soc. János Bolyai, Szeged 30 II (1979), 709–740. 
MR 0680616 
[10] Mawhin, J.: 
Topological Degree Methods in Nonlinear Boundary Value Problems. CBMS Series, Amer. Math. Soc., Providence, RI 40 (1979). 
MR 0525202 | 
Zbl 0414.34025 
[12] Mawhin, J., Ward Jr., J. R.: 
Guiding-like functions for periodic or bounded solutions of ordinary differential equations. Discrete Contin. Dynam. Systems 8 (1) (2002), 39–54. 
MR 1877827 | 
Zbl 1087.34518 
[13] Scorza Dragoni, G.: Intorno a un criterio di esistenza per un problema di valori ai limiti. Rend. Accad. Naz. Lincei 28 (6) (1938), 317–325.
[14] Taddei, V., Zanolin, F.: 
Bound sets and two-points boundary value problems for second order differential equations. Georg. Math. J., Special issue dedicated to 70th birthday of Prof. I. Kiguradze 14 (2) (2007). 
MR 2341286