Mughatil ibn Atieh Bakri (مقاتل بن عطیه بکری) was allegedly a Medieval authority of the Al-Nizamiyya of Baghdad, and son in law of Nizam al-Mulk. He is known only by a treatise that he wrote, in which he recounts in detail a Sunni - Shia debate taking place in the court of Sultan Malik Shah I.
The text was written in Arabic under the title "مؤتمرعلماء بغداد" and has been translated into Persian under the title In search of Truth in Baghdad (در جستجوی حق در بغداد). It has also appeared under the title "راهي به سوي حقيقت" with ISBN . The text's authenticity is under question, as well as its attribution to ibn Atieh Bakri because few copies of it were known and all from centuries after the death of Mughatil.
More info on Bakri's book: (in Persian). Note that the groups of numbers in the ISBN may appear in reverse order when viewing the catalog of an Iranian bookstore, due to the writing convention.