“…for superstring orbifolds of permutation-type. There is a surprisingly large variety of orbifolds of permutation-type, including the permutation orbifolds themselves [1][2][3][4][5][6]11,16], the orientation orbifolds [12,13,15,16], the open-string permutation orbifolds [14] and their T -duals [15,16], the generalized permutation orbifolds [15,16] and others. A short review of these varieties is included in Ref.…”