“…Since W algebras [1,2] received considerable attention and application, much work [3,4,5,6,7,8,9,10] has been carried out on the classification of W algebras and the study of W gravities and W strings. In fact, W algebras also imply some underlying symmetry and appear in the quantum Hall effect [11] and black holes [12,13], in lattice models of statistical mechanics at criticality, and in other physical models [14,15] and so on.…”