“…In fact, the study of scalar equations had really started in the middle of 80s by M.Ôtani [34] in one dimension and then in dimension N by F. de Thélin [19]. Later, the results are generalized to other kinds of equations or systems involving p-Laplacian in R N or bounded open set Ω ⊂ R N (see, e.g., [1,3,4,5,6,7,8,13,18,20,23,24,27,29,30,33,35] and the references therein).…”