Kitab al-Kafi
Little was known of Aaron until Adolf Neubauer discovered, among the manuscript collection of Abraham Firkovitch in St. Petersburg, important fragments in Arabic of the "Mushtamil" (The Comprehensive), a Hebrew grammar consisting of eight books. Bacher, while studying these fragments, succeeded in rediscovering the unknown grammarian. S. Poznanski published some valuable specimens of Aaron's work; and, following a suggestion of Abraham Harkavy, he threw new light on the author and some other works of his: namely, the "Kitab al-Kafi", a commentary on the Pentateuch, often quoted by Karaite writers, and a lexicographical work bearing the title "Sharḥ Alalfaẓ," a part of which is extant in the British Museum.