reserve x,y,z,c for object,
  f for Function of 2-tuples_on BOOLEAN, BOOLEAN;
reserve s for State of 2GatesCircuit(x,y,c,f);

theorem
  InnerVertices BitAdderWithOverflowStr(x,y,c) is Relation
proof
  InnerVertices 2GatesCircStr(x,y,c, 'xor') is Relation & InnerVertices
  MajorityStr(x,y,c) is Relation by Th58,Th67;
  hence thesis by Th2,CIRCCOMB:47;
end;
