http://esl.fis.edu/grammar/multi/r1.htm
http://www.ihbristol.com/free-english-exercises/test/esol-smc-past-tenses
http://www.ihbristol.com/free-english-exercises/test/esol-smc-more-mixed-tenses
https://www.ego4u.com/en/cram-up/tests/language-course
http://sites.uclouvain.be/gramlink/Gramlink-AN/exercices/passe/mixed/mix01.htm
http://www.learnenglishfeelgood.com/mixed-verb-tenses5.html
http://www.learnenglishfeelgood.com/mixed-verb-tenses4.html
http://www.learnenglishfeelgood.com/mixed-verb-tenses3.html
http://www.englishgrammarsecrets.com/pastreview2/exercise5.swf
http://www.englishgrammarsecrets.com/pastreview2/exercise2.swf