@inproceedings{ CASTRO,
author = { ENRIQUE CASTRO MARTINEZ } ,
title = { Dificultad en problemas de estructura multiplicativa de comparaciĆ³n },
booktitle = { 15th Conference of the International Group for the Psychology of Mathematics Education },
year = { 1991 },
pages = { None - None },
location = { ASSISI, ITALIA },
}