theorem Th14:
  i mod p is Element of GF(p)
  proof
    reconsider b = i mod p as Integer;
    b in NAT by INT_1:3,57;
    then reconsider b as Nat;
    b<p by INT_1:58;
    then b in Segm(p) by NAT_1:44;
    hence thesis;
  end;
