Stern derives a further result from the published text of the "Kitāb al-Imtā wa 'l-Mu'anasa", pointing out that a story al-Tawhīdī ascribes to a personal meeting with Qadi Abu'l-Hasan 'Alī b. Hārūn az-Zanjāni, the founder of the group, appears in almost identical form in one of the epistles. While neat, Stern's view of things has been challenged by Tibawi, who points out some assumptions and errors Stern has made, such as the relationship between the story in al-Tawhīdī's work and the Epistles; Tibawi points out the possibility that the story was instead taken from a third, independent and prior source.