@article{2003-Leijenhorst-HeapsLaw,
  author		= "Leijenhorst, D.C. van and Weide, Th.P. van der and Grootjen, F.A.",
  title			= "{A formal derivation of Heaps` Law}",
  journal		= "Information Sciences",
  number		= "--",
  year			= "2003",
  code			= "icis.NIII-R0302",
  research_group	= "iris",
  pages			= "--",
  class			= "Journal"
}