It is "(a) history of the Bábí movement up to 1852. Nicolas gives a list of sources for this book on pp. 48-53. It is interesting to note that among his oral sources are four of the leading Bahá'ís of that period, who had been designated by Bahá'u'lláh as 'Hands of the Cause': Mírzá 'Alí-Muhammad, 'Ibn-i-Asdaq: Mullá 'Al-Akbar-i-Sháhmírzádí, Hají Akhund; Mírzá Muhammad-Táqíy-i-Abharí, 'Ibn-i-Abhar; and Mírzá Hasan-i-Adíb. The other two oral sources named are Siyyid 'Ismu'lláh, who was presumably Siyyid Mihdíy-i-Dihají, and Mírzá Yahyá, Subh-i-Azál." [BBR38-39]