@TECHREPORT\{IMM1992-02774,
    author       = "M. Rostgaard and N. K. Poulsen and O. Ravn",
    title        = "A rapprochement Between Discrete-time operators",
    year         = "1992",
    number       = "15",
    series       = "",
    institution  = "Institute of Mathematical Statistics and Operations Research (IMSOR), The Technical University of Denmark",
    address      = "",
    type         = "",
    note         = "Also in ECC93 pp. 426-431, 1993",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/2774-full.html"
}