theorem
  Lang(A) = right-Lang(the InitS of A)
proof
A1: w in Lang(A) implies w in right-Lang(the InitS of A)
  proof
    assume w in Lang(A);
    then w-succ_of (the InitS of A, A) meets (the FinalS of A) by Th19;
    hence thesis;
  end;
  w in right-Lang(the InitS of A) implies w in Lang(A)
  proof
    assume w in right-Lang(the InitS of A);
    then w-succ_of (the InitS of A, A) meets (the FinalS of A) by Th17;
    hence thesis by Th19;
  end;
  hence thesis by A1,SUBSET_1:3;
end;
