theorem
  modRel(4) = {[0,1], [1,2], [2,3], [3,0]}
proof
  thus modRel(4) = succRel(4) \/ {[4-1,0]} by Th41
    .= {[0,1], [1,2], [2,3], [3,0]} by Th8, ENUMSET1:6;
end;
