{{Cite| last1 = Larmarange| first1 = Joseph| last2 = Ludecke| first2 = Daniel| last3 = Wickham| first3 = Hadley| title = labelled: Manipulating Labelled Data| access-date = 2016-06-12| date = 2016-06-01| url = https://cran.r-project.org/web/packages/labelled/index.html}}