BibTeX:
@incollection{JulietThompson1947,
  author = {Juliet Thompson},
  title = {Be Happy in the Present},
  booktitle = {The Diary of Juliet Thompson},
  year = {1947},
  publisher = {Kalimát Press},
  url = {https://bahai-library.com/thompson_diary},
}

APA:
Juliet Thompson. (1947). Be Happy in the Present. In *The Diary of Juliet Thompson*. Kalimát Press.

MLA:
Juliet Thompson. "Be Happy in the Present." *The Diary of Juliet Thompson*, Kalimát Press, 1947.

Chicago:
Juliet Thompson. "Be Happy in the Present." In *The Diary of Juliet Thompson*, Kalimát Press, 1947.