Peter J. Rousseeuw and Ida Ruts and John W. Tukey.
The Bagplot: A Bivariate Boxplot.
In The American Statistician, vol. 53, no. 4, pp. 382--287, 1999.

Bibtex:

@Article{        rousseeuw:1999:TBBB,
  author = 	 "Peter J. Rousseeuw and Ida Ruts and John W. Tukey",
  title = 	 "The Bagplot: A Bivariate Boxplot",
  journal = 	 "The American Statistician",
  year = 	 "1999",
  volume = 	 "53",
  number = 	 "4",
  pages = 	 "382--287",
  month = 	 "November",
}