“…To our knowledge, the double-graded quantum superplane is the first such example to be defined and studied. We must remark that there has been some renewed interest in Z n 2 -gradings in physics, see for example [1,2,3,9,37,38]. It is not clear if these 'higher gradings' play a fundamental rôle in physics in the same way as Z 2 -gradings do.…”