@article{PM_2007_2007_1_a21,
     author = {Gu\`ardia, Jordi},
     title = {Thetanullwerte: de periodos a buenas ecuaciones.},
     journal = {Publicacions matem\`atiques},
     publisher = {mathdoc},
     year = {2007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PM_2007_2007_1_a21/}
}