“…These works extended the notion of ordinary, Z 2 -graded, Lie superalgebras appearing in [18] and suggested possible applications to elementary particles. Ever since the mathematical aspects (including classifications, representations, etc) of the Z 2 × Z 2 -graded Lie superalgebras and of their generalizations have been constantly investigated, see [19][20][21][22][23][24][25][26][27][28][29]. In physics Z 2 × Z 2 -graded Lie superalgebras have been studied in the contexts of de Sitter spaces [30][31][32], quasispin [33], strings [34], extension of Poincaré algebras [35,36], double field theories [37], mixed tensors [38,39].…”