@article{GeoVra:69b,
  journal = {Rev. Roumaine Math. Pures Appl.},
  volume = {14},
  title = {{$r$}-valent centered {L}ukasiewicz algebras},
  author = {Georgescu, George and Vraciu, Constantin},
  year = {1969},
  fjournal = {Acad\'emie de la R\'epublique Populaire Roumaine. Revue Roumaine
              de Math\'ematiques Pures et Appliqu\'ees},
  pages = {793--802},
}