1. Armstrong, S.N., Tran, H.V.: Viscosity solutions of general viscous Hamilton–Jacobi equations. Math. Ann. 361, 647–687 (2015)
2. Barles, G.: A weak Bernstein method for fully non-linear elliptic equations. Differ. Integral Equ. 4(2), 241–262 (1991)
3. Barles, G.: Local gradient estimates for second-order nonlinear elliptic and parabolic equations by the weak Bernstein’s method
4. Berestycki, H., Caffarelli, L. A., Nirenberg, L.: Further qualitative properties for elliptic equations in unbounded domains. Ann. Scuola Norm. Sup. Pisa Cl. Sci. (4), 25(1–2), 69–94 (1998)
5. Berestycki, H., Caffarelli, L., Nirenberg, L.: Symmetry for elliptic equations in a half-space In: Lions, J.L. et al. (eds.), Boundary Value Problems for Partial Differential Equations and Applications, RMA Res. Notes Appl. Math., vol. 29, Masson, Paris, pp. 27–42 (1993)