“…In recent years equations of the type (1) have been the subject of rather deep investigations since appears from many branches of mathematics and applied mathematics. For more surveys on these questions we advise the paper of Alves and Holanda [1], Bao-Ji and Li [3], Bandle and Giarrusso [2], Cirstea and Rȃdulescu [4], Clément-Manásevich and Mitidieri [5], De Figueiredo and Jianfu [6], Galaktionov and Vázquez [7], Ghergu and Rȃdulescu [8], Salani [19], Ji and Bao [12], Jian [11], Peterson and Wood [16], Quittner [17], Li and Yang [13], Li-Zhang and Zhang [14], Viaclovsky [20,21] and not the last Zhang and Zhou [22].…”