@ARTICLE\{IMM2007-03617,
    author       = "R. K. Olsson and K. B. Petersen and T. Lehn-Schi{\o}ler",
    title        = "State-space models - from the {EM} algorithm to a gradient approach",
    year         = "2007",
    keywords     = "{EM,} state-space models, quasi-Newton",
    pages        = "1097-1111",
    journal      = "Neural Computation",
    volume       = "19",
    editor       = "",
    number       = "4",
    publisher    = "",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/3617-full.html"
}