http://www.erin.utoronto.ca/~hgezundh/grammaire/exercices/ex-comparatifs.html
http://www.lepointdufle.net/p/comparaison.htm
http://www.didieraccord.com/exercices/index.php?ex=3.1.6
http://www.mesexercices.com/exercices/exercice-culture-2/exercice-culture-38572.php