Modals

1. http://a4esl.org/q/h/0101/ig-modals.html
2. http://www.eslus.com/LESSONS/GRAMMAR/MODALS/Modala.htm
3. http://www.eslus.com/LESSONS/GRAMMAR/MODALS/Gramb.htm
4. http://www.eslcafe.com/quiz/modal1.html
5. http://grammar.ccc.commnet.edu/grammar/cgi-shl/quiz.pl/modal_quiz.htm