@techreport{
    hajn:99a,
    author = "Hajnicz, Elżbieta",
    title = "Defining intervals by means of point skeletons: generalization of pairs of points",
    year = "1999",
    number = "900",
    address = "Warsaw",
    type = "{IPI PAN} Research Report",
    institution = "Institute of Computer Science, Polish Academy of Sciences"
}