Last week I was visiting my colleague prof. Eugenio Mijangos at the Dept. of App. Maths, Statistics and OR in the University of the Basque Country, Bilbao During the stay we had the opportunity of working together in several projects related with the resolution of some MINLP arising in the optimization of the electricity market models developped in the research project DPI2008-02153. I really enjoied both the working sessions with Eugenio and the city of Bilbao.