Explanation:
1. http://www.englishclub.com/grammar/verbs-m_used-to-do.htm
2. http://www.englishteachermelanie.com/grammar-how-to-use-used-to/
3. http://www.englishpage.com/verbpage/usedto.html
Exercises:
1. http://www.perfect-english-grammar.com/used-to-exercise-1.html
2. https://elt.oup.com/student/solutions1stedition/int_unit_page/unit2/grammar/exercise2?mode=hub&cc=tr&selLanguage=en
3. http://ingles.ing.uchile.cl/otros/Used%20to%201.pdf
Video:
1. http://www.youtube.com/watch?v=qJMhHSTBwwY
1. http://www.englishclub.com/grammar/verbs-m_used-to-do.htm
2. http://www.englishteachermelanie.com/grammar-how-to-use-used-to/
3. http://www.englishpage.com/verbpage/usedto.html
Exercises:
1. http://www.perfect-english-grammar.com/used-to-exercise-1.html
2. https://elt.oup.com/student/solutions1stedition/int_unit_page/unit2/grammar/exercise2?mode=hub&cc=tr&selLanguage=en
3. http://ingles.ing.uchile.cl/otros/Used%20to%201.pdf
Video:
1. http://www.youtube.com/watch?v=qJMhHSTBwwY