@TECHREPORT\{IMM1989-03831,
    author       = "V. V. Vidal",
    title        = "The generalized maximum principle: an introduction",
    year         = "1989",
    pages        = "19",
    number       = "",
    series       = "",
    institution  = "{IMSOR,} {DTH}",
    address      = "",
    type         = "",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/3831-full.html"
}