Hastie, T. and Stuetzle, W., [Principal Curves](https://www.jstor.org/stable/2289936), JASA, Vol. 84, No. 406 (Jun., 1989), pp. 502-516.<doi:10.2307/2289936> [[PDF](https://www.jstor.org/stable/2289936})]

Corresponding BibTeX entry:

  @Article{,
    author = {Trevor Hastie and Werner Stuetzle},
    title = {Principal Curves},
    journal = {Journal of the American Statistical Association},
    year = {1989},
    month = {June},
    volume = {84},
    number = {406},
    pages = {502-516},
    doi = {10.2307/2289936},
    url = {https://www.jstor.org/stable/2289936},
    note =
      {\url{https://web.stanford.edu/~hastie/Papers/principalcurves.pdf}},
  }