BibTeX:
@incollection{JulietThompson,
  author = {Juliet Thompson},
  title = {Two Arts},
  booktitle = {The Diary of Juliet Thompson},
}

APA:
Juliet Thompson. Two Arts. In *The Diary of Juliet Thompson*.

MLA:
Juliet Thompson. "Two Arts." *The Diary of Juliet Thompson*, n.d..

Chicago:
Juliet Thompson. "Two Arts." In *The Diary of Juliet Thompson*, n.d..