@TECHREPORT\{IMM1992-02775,
    author       = "M. Rostgaard and N. k. Poulsen and O. Ravn",
    title        = "Spectral factorization using the delta operator",
    year         = "1992",
    number       = "14",
    series       = "",
    institution  = "Institute of Mathematical Statistics and Operations Research (IMSOR), The Technical University of Denmark",
    address      = "",
    type         = "",
    note         = "Also in Systems and Control Letter pp. 293-301, 1994",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/2775-full.html"
}