BibTeX:
@incollection{Various,
  author = {Various},
  title = {The Children's Festival at Esslingen},
  booktitle = {Baha'i Stories for Children},
  url = {https://bahaistoriesforchildren.blogspot.com/2023/09/abdul-bahas-meeting-with-children-in.html},
}

APA:
Various. The Children's Festival at Esslingen. In *Baha'i Stories for Children*.

MLA:
Various. "The Children's Festival at Esslingen." *Baha'i Stories for Children*, n.d..

Chicago:
Various. "The Children's Festival at Esslingen." In *Baha'i Stories for Children*, n.d..