BibTeX:
@incollection{JEEsslemont1923,
  author = {J. E. Esslemont},
  title = {Mashriqu’l-Adhkár34},
  booktitle = {Bahá'u'lláh and the New Era},
  year = {1923},
  url = {https://www.gutenberg.org/cache/epub/19241/pg19241-images.html},
}

APA:
J. E. Esslemont. (1923). Mashriqu’l-Adhkár34. In *Bahá'u'lláh and the New Era*.

MLA:
J. E. Esslemont. "Mashriqu’l-Adhkár34." *Bahá'u'lláh and the New Era*, 1923.

Chicago:
J. E. Esslemont. "Mashriqu’l-Adhkár34." In *Bahá'u'lláh and the New Era*, 1923.