Francisco Echarte José Javier Astrain Alberto Córdoba Jesús E. Villadangos Ontology of Folksonomy: A New Modelling Method. 2007 SAAKM http://ceur-ws.org/Vol-289/p08.pdf conf/kcap/2007saakm db/conf/kcap/saakm2007.html#EcharteACV07