You are reading an old version of the documentation (v1.2.1). For the latest version see https://matplotlib.org/stable/citing.html
matplotlib

Citing matplotlib

If matplotlib contributes to a project that leads to a scientific publication, please acknowledge this fact by citing the project. You can use this BibTeX entry:

@Article{Hunter:2007,
  Author    = {Hunter, J. D.},
  Title     = {Matplotlib: A 2D graphics environment},
  Journal   = {Computing In Science \& Engineering},
  Volume    = {9},
  Number    = {3},
  Pages     = {90--95},
  abstract  = {Matplotlib is a 2D graphics package used for Python
  for application development, interactive scripting, and
  publication-quality image generation across user
  interfaces and operating systems.},
  publisher = {IEEE COMPUTER SOC},
  year      = 2007
}