theorem Th69:
  not x in still_not-bound_in p implies (p 'or' All(x,q)) <=> All(
  x,p 'or' q) is valid
proof
  assume not x in still_not-bound_in p;
  then (p 'or' All(x,q)) => All(x,p 'or' q) is valid & All(x,p 'or' q) => (p
  'or' All(x,q)) is valid by Th68;
  hence thesis by Lm14;
end;
