BibTeX:
@incollection{Various,
  author = {Various},
  title = {Happy Holidays!},
  booktitle = {Baha'i Stories for Children},
  url = {https://bahaistoriesforchildren.blogspot.com/2017/02/happy-holidays.html},
}

APA:
Various. Happy Holidays!. In *Baha'i Stories for Children*.

MLA:
Various. "Happy Holidays!." *Baha'i Stories for Children*, n.d..

Chicago:
Various. "Happy Holidays!." In *Baha'i Stories for Children*, n.d..