@ARTICLE\{IMM1997-01866,
    author       = "A. E. Haxthausen",
    title        = "Order-sorted Algebraic Specifications   with Higher-order Functions",
    year         = "1997",
    pages        = "157-185",
    journal      = "Theoretical Computer Science",
    volume       = "183",
    editor       = "",
    number       = "",
    publisher    = "",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/1866-full.html"
}