associations: 4

mode  bc  el1 - local vertices <->  el2 - local vertices
 1   -1   0      2 0       3   0 2 
 1   -1   4      2 0       7   0 2 
 1   -2   1      2 1       4   1 2 
 1   -2   3      2 1       6   1 2