Musannaf Ibn Abi Shayba 26:31

Abu Khalid narrated to us, from Hajjaj, from a sheikh, from Ibn al-Hanafiyyah regarding a woman and two parents: The woman receives a fourth, and the mother receives a third of what remains. Abu Bakr said: This is from four shares. For the woman is one share, which is the fourth. For the mother is a third of what remains, which is one share. And for the father are two shares.