EXPLORATORY STUDY ON THE IBERIAN UNION IN SECONDARY TEXTBOOKS OF PORTUGAL AND SPAIN: STUDENTS' IDEAS ABOUT THIS HISTORICAL PROCESS FROM THEIR USE Glória Solé (CIEd, University of Minho, Portugal) gsole@ie.uminho.pt Cosme Gómez (DICSO, University of Múrcia, Spain) cjgomez@um.es