@misc{74070,
  author = {Mike Cullen},
  title = {Use of potential vorticity as a control variable within a 4D variational data assimilation system},
  year = {2002},
  journal = {ECMWF Technical Memoranda},
  number = {358},
  pages = {21},
  month = {01/2002},
  publisher = {ECMWF},
  address = {Shinfield Park, Reading},
  url = {https://www.ecmwf.int/node/8833},
  doi = {10.21957/9n5pw7izh},
  language = {eng},
}