Parzen, Emanuel.
On Estimation of a Probability Density Function and Mode.
In The Annals of Mathematical Statistics, vol. 33, no. 3, pp. 1065--1076, 1962.

Bibtex:

@Article{        parzen:1962:PDFM,
  author =       "Parzen, Emanuel",
  journal =      "The Annals of Mathematical Statistics",
  number =       "3",
  pages =        "1065--1076",
  title =        "On Estimation of a Probability Density Function and Mode",
  volume =       "33",
  year =         "1962",
}