All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and messenger.
As far as we know, Abu Haneefah did not author a book entitled Al-Aathaar, but there is a book titled Al-Aathaar by his student Abu Yoosuf Ibraaheem ibn Ya’qoob Al-Ansaari, who died in 182 A.H.
Moreover, his other student Muhammad ibn Al-Hasan Ash-Shaybaani, who died in 189 A.H. authored a book entitled Al-Aathaar.
For more benefit, please refer to Fatwa 88718.
Allaah Knows best.