BibTeX:
@incollection{JEEsslemont1923,
  author = {J.E. Esslemont},
  title = {Why We Say Ascension: The Setting of the Sun and the Pilgrim Road to Bahjí},
  booktitle = {Bahá'u'lláh and the New Era},
  year = {1923},
  publisher = {Bahá'í Publishing Trust},
  url = {https://www.bahai.org/library/other-literature/publications-individual-authors/bahaullah-new-era/},
}

APA:
J.E. Esslemont. (1923). Why We Say Ascension: The Setting of the Sun and the Pilgrim Road to Bahjí. In *Bahá'u'lláh and the New Era*. Bahá'í Publishing Trust.

MLA:
J.E. Esslemont. "Why We Say Ascension: The Setting of the Sun and the Pilgrim Road to Bahjí." *Bahá'u'lláh and the New Era*, Bahá'í Publishing Trust, 1923.

Chicago:
J.E. Esslemont. "Why We Say Ascension: The Setting of the Sun and the Pilgrim Road to Bahjí." In *Bahá'u'lláh and the New Era*, Bahá'í Publishing Trust, 1923.