 reserve X,a,b,c,x,y,z,t for set;
 reserve R for Relation;

theorem :: Proposition 13 (7L")
  for R being finite negative_alliance non empty RelStr,
      X being Subset of R holds
    (LAp X)` c= LAp ((LAp X)`)
  proof
    let R be finite negative_alliance non empty RelStr;
    for X being Subset of R holds UAp ((UAp X)`) c= (UAp X)` by Prop13H;
    hence thesis by Conv;
  end;
