@article{PNA_2007_2007_1_a2,
     author = {Fr{\'\i}as, Antonio and  Castro, Enrique},
     title = {Influencia del {N\'umero} de {Conexiones} en la {Representaci\'on} {Simb\'olica} de {Problemas} {Aritm\'eticos} de dos {Pasos.}},
     journal = {PNA},
     pages = {29-41},
     publisher = {mathdoc},
     volume = {2},
     number = {1},
     year = {2007},
     language = {es},
     url = {http://geodesic.mathdoc.fr/item/PNA_2007_2007_1_a2/}
}