BibTeX:
@incollection{MrzMamdiZarqn1998,
  author = {Mírzá Maḥmúd-i-Zarqání},
  title = {Philadelphia: 'Abdu'l-Bahá at the Baptist Temple},
  booktitle = {Mahmúd's Diary: The Diary of Mírzá Maḥmúd-i-Zarqání},
  year = {1998},
  publisher = {George Ronald},
}

APA:
Mírzá Maḥmúd-i-Zarqání. (1998). Philadelphia: 'Abdu'l-Bahá at the Baptist Temple. In *Mahmúd's Diary: The Diary of Mírzá Maḥmúd-i-Zarqání*. George Ronald.

MLA:
Mírzá Maḥmúd-i-Zarqání. "Philadelphia: 'Abdu'l-Bahá at the Baptist Temple." *Mahmúd's Diary: The Diary of Mírzá Maḥmúd-i-Zarqání*, George Ronald, 1998.

Chicago:
Mírzá Maḥmúd-i-Zarqání. "Philadelphia: 'Abdu'l-Bahá at the Baptist Temple." In *Mahmúd's Diary: The Diary of Mírzá Maḥmúd-i-Zarqání*, George Ronald, 1998.