Sepher Ha'Aruch [Talmudic dictionary]

Nathan of Rome’s Aruch is “a manifestation not only of its author’s brilliance and deep acquaintance with sources, but also of his encyclopaedic knowledge. Indeed, in some instances it is the sole source for ancient traditions of Talmudic interpretation.” S. B. Linderman, Sefer Sarid ba-Arachin (1972), Introduction. See also M.J. Heller, The Sixteenth Century Hebrew Book (2004) pp. 104-5.