@article{ASENS_2005_4_38_5_751_0,
     author = {Acquistapace, Francesca and Broglia, Fabrizio and Fernando, Jos\'e F. and Ruiz, Jes\'us M.},
     title = {On the pythagoras numbers of real analytic surfaces},
     journal = {Annales scientifiques de l'\'Ecole Normale Sup\'erieure},
     pages = {751--772},
     publisher = {Elsevier},
     volume = {Ser. 4, 38},
     number = {5},
     year = {2005},
     doi = {10.1016/j.ansens.2005.04.001},
     mrnumber = {2195258},
     zbl = {1087.32003},
     language = {en},
     url = {http://archive.numdam.org/articles/10.1016/j.ansens.2005.04.001/}
}