reserve i,n,m,k,x for Nat,
  i1,i2 for Integer;

theorem Th10:
  k-SD_Sub_S c= INT
proof
  let e be object;
  assume
A1: e in k-SD_Sub_S;
  k-SD_Sub_S c= k-SD_Sub by Th2;
  then e is Integer by A1,Th8;
  hence thesis by INT_1:def 2;
end;
