Hebrew Philology.
Steinschneider.—Jewish Literature, p. 131.
Chazars.
Letter of Chasdai to Chazars (Engl. transl. by Zedner, Miscellany of the Society of Hebrew Literature, Vol. I).
Graetz.—III, p. 138 [140].
Samuel Ibn Nagdela.
Graetz,—III, p, 254 [260].