@BOOK\{IMM1987-03752,
    author       = "V. V. Vidal and H. Ravn and Z. Nahorski",
    title        = "Properties of upper boundary functions in discrete time optimal control",
    year         = "1987",
    pages        = "200",
    volume       = "",
    number       = "",
    series       = "",
    publisher    = "{IMSOR,} {DTH}",
    address      = "",
    edition      = "",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/3752-full.html"
}