theorem
  Valid('not'(p '&' 'not' p),J).v = TRUE
proof
  Valid('not'(p '&' 'not' p),J).v = 'not'(Valid(p '&' 'not' p,J).v) by Th10
    .= 'not' FALSE by Th14;
  hence thesis by MARGREL1:11;
end;
