[1] Amster, P., Haddad, J.: 
A Hartman-Nagumo type condition for a class of contractible domains. Topol. Methods Nonlinear Anal. 41 (2013), 287-304. 
MR 3114309 | 
Zbl 1306.34033 
[2] Bass, R. W.: 
On non-linear repulsive forces. Contributions to the Theory of Nonlinear Oscillations, Volume IV. Annals of Mathematics Studies 41. Princeton University Press, Princeton (1958), 201-211 S. Lefschetz. 
DOI 10.1515/9781400881758-011 | 
MR 0100704 | 
Zbl 0083.31405 
[3] Bebernes, J. W.: 
A simple alternative problem for finding periodic solutions of second order ordinary differential systems. Proc. Am. Math. Soc. 42 (1974), 121-127. 
DOI 10.2307/2039687 | 
MR 0330597 | 
Zbl 0286.34055 
[4] Bernstein, S. N.: 
Sur les équations du calcul des variations. Ann. Sci. Éc. Norm. Supér., Sér. III. 29 (1912), 431-485 French \99999JFM99999 43.0460.01. 
DOI 10.24033/asens.651 | 
MR 1509153 
[10] Frigon, M.: 
Boundary and periodic value problems for systems of differential equations under Bernstein-Nagumo growth condition. Differ. Integral Equ. 8 (1995), 1789-1804. 
MR 1347980 | 
Zbl 0831.34021 
[15] Henderson, J., Sheng, Q., Tisdell, C. C.: 
Constructive existence results for solutions to systems of boundary value problems via general Lyapunov methods. Differ. Equ. Appl. 9 (2017), 57-68. 
DOI 10.7153/dea-09-05 | 
MR 3610874 | 
Zbl 1365.34043 
[22] Nagumo, M.: 
Über die Differentialgleichung $y'' = f(t, y, y')$. Proc. Phys.-Math. Soc. Japan, III. Ser. 19 (1937), 861-866 German. 
Zbl 0017.30801 
[24] Rouche, N., Mawhin, J.: 
Équations différentielles ordinaires. Tome I: Théorie générale. Tome II: Stabilité et solutions périodiques. Masson et Cie, Paris French (1973). 
MR 0481182 | 
Zbl 0289.34001 
[27] Taddei, V.: 
Two-points boundary value problems for Carathéodory second order equations. Arch. Math., Brno 44 (2008), 93-103. 
MR 2432846 | 
Zbl 1212.34039 
[30] Tisdell, C. C., Tan, L. H.: 
On vector boundary value problems without growth restrictions. JIPAM, J. Inequal. Pure Appl. Math. 6 (2005), Article No. 137, 10 pages \99999MR99999 2191606 \filbreak. 
MR 2191606 | 
Zbl 1097.34018