To cite monotone in publications use:

Busing FMTA (2022). “Monotone Regression: A Simple and Fast O(n) PAVA Implementation.” Journal of Statistical Software, Code Snippets, 102(1), 1–25. doi:10.18637/jss.v102.c01.

Corresponding BibTeX entry:

  @Article{,
    title = {Monotone Regression: A Simple and Fast O(n) PAVA
      Implementation},
    author = {Frank M. T. A. Busing},
    journal = {Journal of Statistical Software, Code Snippets},
    year = {2022},
    volume = {102},
    number = {1},
    pages = {1--25},
    doi = {10.18637/jss.v102.c01},
  }