Here's the original paper: "A pattern-matching algorithm for two-dimensional coordinate lists" by E. J. Groth, 1986 http://adsabs.harvard.edu/abs/1986AJ.....91

Here's the original paper: "A pattern-matching algorithm for two-dimensional coordinate lists" by E. J. Groth, 1986 http://adsabs.harvard.edu/abs/1986AJ.....91.1244G http://adsabs.harvard.edu/abs/1986AJ.....91.1244G