@incollection{Elliott91:SemiFunctional,
    author = "Conal Elliott and Frank Pfenning",
    title = {A Semi-Functional Implementation of a Higher-Order Logic Programming Language},
    url = {http://conal.net/papers/elpsml.pdf},
    booktitle = "Topics in Advanced Language Implementation",
    publisher = "MIT Press",
    editor = "Peter Lee",
    year = "1991"
}