@article{Vai:56a,
  journal = {Com. Acad. R. P. Rom\^{\i}ne},
  volume = {6},
  title = {Extension du th\'eor\`eme d'approximation de {K}. {W}eierstrass aux
           fonctions hyperboliques-continues \`a deux variables},
  author = {Vaida, Dragos},
  year = {1956},
  pages = {1173--1178},
}