 reserve a,b for object;
 reserve k,l,m,n for Nat;
 reserve p,q,r,s for FinSequence;
 reserve P for non empty FinSequence-membered set;
 reserve S,T for Polish-language;
 reserve V for Polish-language of T;
 reserve K for non trivial Polish-language;
 reserve E for Polish-arity-function of K;
 reserve B for Polish-arity-function;
 reserve A for Polish-arity-function of T;
 reserve C for Extension of B;
 reserve Z for B-closed Polish-language;
 reserve J for Polish-ext-set of B;

theorem Th8:
  for B, J holds Polish-WFF-set B c= J
proof
  let B, J;
  set T = dom B;
  set V = Polish-WFF-set B;
  reconsider A = B as Polish-arity-function of T by Th1;
  V = Polish-expression-set(T,A) by Def4;
  hence thesis by POLNOT_1:37;
end;
