Juan Martínez Munuera has taken charge of matches involving Cristiano Ronaldo and Lionel Messi in Spain's La Liga, but on Sunday he has his biggest assignment yet, when he referees the UEFA European Under-19 Championship final.For the 36-year-old Spaniard from Benidorm the match between Italy and Portugal in Seinajoki will be his fifth at the tournament in Finland, two of which have been as referee."For me, it has been a great experience," Martínez Munuera told UEFA.com. "Under-19 matches can be some of the most challenging games in terms of mental focus, because while the players are well-disciplined and also have a high skill level, they are still