BibTeX:
@incollection{MrzMamdiZarqn1998,
  author = {Mírzá Maḥmúd-i-Zarqání},
  title = {Why Not Praise Christ and Muḥammad: 'Abdu'l-Bahá at Temple Emanu-El},
  booktitle = {Mahmúd's Diary: The Diary of Mírzá Maḥmúd-i-Zarqání},
  year = {1998},
  publisher = {George Ronald},
}

APA:
Mírzá Maḥmúd-i-Zarqání. (1998). Why Not Praise Christ and Muḥammad: 'Abdu'l-Bahá at Temple Emanu-El. In *Mahmúd's Diary: The Diary of Mírzá Maḥmúd-i-Zarqání*. George Ronald.

MLA:
Mírzá Maḥmúd-i-Zarqání. "Why Not Praise Christ and Muḥammad: 'Abdu'l-Bahá at Temple Emanu-El." *Mahmúd's Diary: The Diary of Mírzá Maḥmúd-i-Zarqání*, George Ronald, 1998.

Chicago:
Mírzá Maḥmúd-i-Zarqání. "Why Not Praise Christ and Muḥammad: 'Abdu'l-Bahá at Temple Emanu-El." In *Mahmúd's Diary: The Diary of Mírzá Maḥmúd-i-Zarqání*, George Ronald, 1998.