@phdthesis{74676,
  author = {N. Gustafsson},
  title = {Use of a digital filter as a weak constraint in variational data assimilation},
  year = {1992},
  journal = {Workshop on Variational Assimilation, with special emphasis on Three-dimensional Aspects, 9-12 November 1992},
  pages = {327-338},
  month = {1992},
  publisher = {ECMWF},
  address = {Shinfield Park, Reading},
  language = {eng},
}