Angelo Ciaramella Witold Pedrycz Alfredo Petrosino Uninorm Based Fuzzy Network for Tree Data Structures. 77-84 2009 WILF http://dx.doi.org/10.1007/978-3-642-02282-1_10 conf/wilf/2009 db/conf/wilf/wilf2009.html#CiaramellaPP09