A New Kind of Graded Lie Algebra and Parastatistical Supersymmetry
  In this paper the usual $Z_2$ graded Lie algebra is generalized to a new form, which may be called $Z_{2,2}$ graded Lie algebra. It is shown that there exists close connections between the $Z_{2,2}$ graded Lie algebra and parastatistics, so the $Z_{2,2}$ can be used to study and analyse various symmetries and supersymmetries of the paraparticle systems. 
Wei Min Yang and Si Cong Jing