BibTeX:
@incollection{Various,
  author = {Various},
  title = {When Gran’pa was a tramp},
  booktitle = {Baha'i Stories for Children},
  url = {https://bahaistoriesforchildren.blogspot.com/2015/03/when-granpa-was-tramp.html},
}

APA:
Various. When Gran’pa was a tramp. In *Baha'i Stories for Children*.

MLA:
Various. "When Gran’pa was a tramp." *Baha'i Stories for Children*, n.d..

Chicago:
Various. "When Gran’pa was a tramp." In *Baha'i Stories for Children*, n.d..