private Sentence transformBiConditionalSentence(BinarySentence bs)
{
Sentence first = new BinarySentence("=>", (Sentence)bs.getFirst()
.accept(this, null), (Sentence)bs.getSecond().accept(this,
null));
Sentence second = new BinarySentence("=>", (Sentence)bs.getSecond()
.accept(this, null), (Sentence)bs.getFirst()
.accept(this, null));
return new BinarySentence("AND", first, second);
}