BibTeX:
@incollection{Various,
  author = {Various},
  title = {Thomas Breakwell's Letters to the Master},
  booktitle = {bahaistories.com archive},
  url = {https://bahaistories.com/subject/breakwell},
}

APA:
Various. Thomas Breakwell's Letters to the Master. In *bahaistories.com archive*.

MLA:
Various. "Thomas Breakwell's Letters to the Master." *bahaistories.com archive*, n.d..

Chicago:
Various. "Thomas Breakwell's Letters to the Master." In *bahaistories.com archive*, n.d..