http://www.englishexercises.org/makeagame/viewgame.asp?id=2065
http://www.agendaweb.org/exercises/grammar/comparison/comparison-write-2
http://www.english-4u.de/comparison_ex3.htm
http://www.bbc.co.uk/worldservice/learningenglish/youmeus/quiznet/newquiz62.shtml
http://www.1-language.com/englishcourse/unit25_grammar_exs.htm
