@TECHREPORT\{IMM1987-0339, author = "H. Juel and R. F. Love", title = "Duality in constrained location problems", year = "1987", number = "", series = "{IMSOR} Research Report 22/1987", institution = "Institute of Mathematical Statistics and Operations Research, Technical University of Denmark", address = "", type = "", url = "http://www2.compute.dtu.dk/pubdb/pubs/339-full.html" }