Positional cloning methods?

[Liam Good]

I am interested in "positional cloning methods" and am hoping that one
of the readers could explain the technique to me or provide references,
or both.
                              Thankyou

                                 Liam Good

                                 Dept. Mol. Biol., Gen.
                                 University of Guelph
                                 Guelph, Ont., N1G 2W1
                                 CANADA