matita/matita/contribs/formal_topology/bin/RES

   1               c
   2    cic
   3  ic    ci             .
   4    ici
   5
   6               i
   7
   8
   9 Con -c = i-  e --p=p:
  10
  11
  12
  13            -i
  14                   -ici
  15    -          -ci      -ic
  16                   -cic
  17            -c