@MISC\{IMM1991-02789,
    author       = "B. G. Thygesen and N. K. Poulsen and J. Holst",
    title        = "A State-Space Description for Sampled Delay Systems using Delta Operator",
    year         = "1991",
    publisher    = "",
    address      = "",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/2789-full.html"
}