“…In [31, pages 477-8], he investigated again the Dirichlet problem of the equation studied by Bernstein, changing analyticity of the domain by smoothness as well as he generalized the results to arbitrary dimensions. More recently, equations of type (2) have been considered, specially for the study of radial solutions and the Dirichlet problem: see, for example, [2,3,11,12,13,14,15,26,27].…”