@incollection{Steffen2022,
  author    = {Joachim Steffen},
  title     = {Variation typology},
  booktitle = {Manual of classification and typology of the Romance languages},
  editor    = {Matthias Heinz and Lorenzo Filipponio and Marc Hinzelin},
  isbn      = {9783110604320},
  year      = {2022},
}