@article{MAN_1991__289_4_164771,
     author = {Jesus J. Ortega},
     title = {On the {Pythagoras} number of a real irreducible algebroid curve.},
     journal = {Mathematische Annalen},
     pages = {111--124},
     publisher = {mathdoc},
     volume = {289},
     number = {4},
     year = {1991},
     zbl = {0743.14041},
     url = {http://geodesic.mathdoc.fr/item/MAN_1991__289_4_164771/}
}