 The Book of Substances (Arabic: Kitab al-Jawahir) is extant only in fragments of Judeo-Arabic (that is, Arabic written in Hebrew letters) in the Firkovitch Collection in St. Petersburg and in the British Museum. Stern established that both manuscripts were separately transliterated from an original text in Arabic characters—which is deducible from transcription errors arising from Arabic rather than Hebrew orthographic similarities, and that the transcription and transliteration errors in the two manuscripts do not match (Stern, “The Fragments of ‘The Book of Substances’”, pp.16–17). Stern pieced together the fragments, adding some missing materials from a passage in “Ibn Hasday’s Neoplatonist” and published them in the Journal of Jewish Studies, vii (1956), 13–29. The extant fragments largely paraphrase and add commentary to passages from the pseudo-Aristotelian “Ibn Hasday’s Neoplatonist.” Due to the close textual proximities between the two texts, Stern conjectured that in places where Israeli is quoting “the philosopher” he is likely quoting a lost passage of the Neoplatonist. These parallels allowed Stern to arrange the discontinuous fragments into an order mirroring its source treatise. Altmann and Stern subsequently published a translation of the fragments in Isaac Israeli, pp. 81–105.