“…For isotropic equations, such problems were investigated by Ghergu and Rȃdulescu [23,24], Haitao [27], Sun, Wu and Long [55] (semilinear equations driven by the Laplacian) and by Giacomoni, Schindler and Takač [25], Papageorgiou, Rȃdulescu and Repovš [40], Papageorgiou, Vetro and Vetro [45], Papageorgiou and Winkert [49]. Very recently, Papageorgiou, Rȃdulescu and Repovš [41] studied isotropic singular problems driven by a more general not necessary homogeneous, differential operator.…”