Helpful links for practice: HAVE TO / MUST

http://www.englishgrammarsecrets.com/musthaveto/menu.php

http://www.englishclub.com/grammar/verbs-modals-have-to-must-not-quiz.htm

http://www.englishpage.com/modals/interactivemodal2.htm

http://ww2.college-em.qc.ca/prof/epritchard/musthavt.htm

http://www.learn-english-today.com/lessons/lesson_contents/must-haveto_ex.html

http://www.better-english.com/grammar/mustnt.htm

http://www.english-area.com/paginas/musthavetoquiz.htm

http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-29834.php

http://www.egeacademy.com/blog/exercises/modal-verbs-exercises-must-have-to/

http://www.englishbee.net/must-have-to-video-lessons-and-exercises/

http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-49540.php