BibTeX:
@incollection{AbdulBah1915,
  author = {'Abdu'l-Bahá},
  title = {The Year of Stress: Nabíl's Grief at the Ascension of Bahá'u'lláh},
  booktitle = {Memorials of the Faithful},
  year = {1915},
  publisher = {Bahá'í Publishing Trust},
  url = {https://www.gutenberg.org/cache/epub/19279/pg19279-images.html},
}

APA:
'Abdu'l-Bahá. (1915). The Year of Stress: Nabíl's Grief at the Ascension of Bahá'u'lláh. In *Memorials of the Faithful*. Bahá'í Publishing Trust.

MLA:
'Abdu'l-Bahá. "The Year of Stress: Nabíl's Grief at the Ascension of Bahá'u'lláh." *Memorials of the Faithful*, Bahá'í Publishing Trust, 1915.

Chicago:
'Abdu'l-Bahá. "The Year of Stress: Nabíl's Grief at the Ascension of Bahá'u'lláh." In *Memorials of the Faithful*, Bahá'í Publishing Trust, 1915.