reserve X1,X2,X3,X4 for set;
reserve n for non zero Nat;
reserve X for non-empty n-element FinSequence;

theorem Thm16:
  for S being SemiringFamily of X holds dom S = dom X
  proof
    let S be SemiringFamily of X;
    dom S = Seg n by FINSEQ_1:89;
    hence thesis by FINSEQ_1:89;
  end;
