<    1,   1, -1,   1, -1, 1,-1;
  -1/4,-1/4,1/4,   0,  0, 0, 0;
     0,   0,  0,-1/4,1/4, 0, 0;
     0,   0,  0,   0,  0,-1, 1;
     0,   0,  0,   0,  0, 1,-1 >