BibTeX:
@incollection{BahsoftheUnitedStateseditors,
  author = {Bahá'ís of the United States editors},
  title = {The First Convention for Amity Between the Races},
  booktitle = {Bahá'ís of the United States},
  url = {https://www.bahai.us/integrating-meetings/},
}

APA:
Bahá'ís of the United States editors. The First Convention for Amity Between the Races. In *Bahá'ís of the United States*.

MLA:
Bahá'ís of the United States editors. "The First Convention for Amity Between the Races." *Bahá'ís of the United States*, n.d..

Chicago:
Bahá'ís of the United States editors. "The First Convention for Amity Between the Races." In *Bahá'ís of the United States*, n.d..