http://suz.digitaleschulebayern.de/english/grammar/comp1.htm
http://www.1-language.com/englishcourse/unit25_grammar_exs2.htm
http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-28752.php
http://www.eslmania.com/students/grammar/Grammar_Quizzes/comparative_superlative.htm
http://s.mound.free.fr/skyblues67/comparing/trig&family2.htm
http://www.english-4u.de/comparison_ex1.htm
http://www.montsemorales.com/gramatica/Comparative.htm
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http://www.esl-lounge.com/student/grammar/3g31-relative-clause-gap-fill-exercise.php
http://www.ego4u.com/en/cram-up/grammar/relative-clauses/exercises?08
http://www.esltower.com/GRAMMARQUIZ/intermediate/relative%20pronoun.htm
http://www.english-area.com/paginas/relativeclauses.htm
http://www.englishexercises.org/makeagame/viewgame.asp?id=1255
