theorem Th33:
  m * n = 122 implies m = 1 & n = 122
                   or m = 2 & n = 61
                   or m = 61 & n = 2
                   or m = 122 & n = 1
  proof
    assume
A1: m*n = 122;
    m divides m*n;
    then m = 1 or m = 2 or m = 61 or m = 122 by A1,Th19;
    hence thesis by A1;
  end;
