N=4 and N=8 SUSY Quantum Mechanics and Klein's Vierergruppe
  Sets of signed permutation matrices satisfying the GR(4,4) algebra are shown to be, up to sign, left cosets of Klein's famous Vierergruppe. In this way we verify the count done by computer in 2012, and set it in a more significant mathematical context. A similar analysis works for GR(1,1), GR(2,2) and GR(8,8). 
S. James Gates and Tristan H\"ubsch and Kevin Iga and Stefan   Mendez-Diez
hep-th math-ph math.GR math.MP