Samuel b. Jacob, who copied the Leningrad Codex, declares expressly that he had copied the Codex from several correct and clear codices which had been prepared by the master Aaron b. Moses b. Asher.
Paul Kahle, The Cairo Geniza (2nd edition, 1959) 110-111
Samuel ben Jacob wrote and pointed and provided with Masora this codex of the Holy Scriptures from the corrected and annotated books prepared by Aaron ben Moses ben Asher the teacher, may his rest be in the Garden of Eden!
Introduction, quoted in E. Wurthwein, The Text of the Old Testament, 2nd ed 1995, p. 180
A certain Samuel b. Jacob copied this Standard Codex of Ben-Asher for Meborach Ibn Osdad. This very important copy is now in the Imperial Public Library at St. Petersburg.
C. D. Ginsburg, Introduction to the Massoretico-Critical Edition of the Hebrew Bible, 1897, p.243
It comprises the single most complete source of all of the Bible books which is closest to the Ben Asher tradition.
Emanuel Tov, Textual Criticism of the Hebrew Bible [Minneapolis: Fortress Press, 2001], p. 47