@article{Gnot:1997,
  author  = "S. Gnot and A. Urbańska-Motyka and R. Zmyślony",
  title   = "Nonnegative maximum likelihood estimation in a linear model of variance components",
  journal = "Discussiones Mathematicae : Algebra and Stochastic Methods",
  volume  = "Vol. 17",
  number  = "no 2",
  pages   = "215--224",
  year    = "1997",
}