BibTeX:
@incollection{AbdulBah1908,
  author = {'Abdu'l-Bahá},
  title = {27: THE TRINITY},
  booktitle = {Some Answered Questions},
  year = {1908},
  url = {https://www.gutenberg.org/cache/epub/19289/pg19289-images.html},
}

APA:
'Abdu'l-Bahá. (1908). 27: THE TRINITY. In *Some Answered Questions*.

MLA:
'Abdu'l-Bahá. "27: THE TRINITY." *Some Answered Questions*, 1908.

Chicago:
'Abdu'l-Bahá. "27: THE TRINITY." In *Some Answered Questions*, 1908.