PAST SIMPLE AND PAST CONTINUOUS
http://www.englishexercises.org/makeagame/viewgame.asp?id=734
http://www.perfect-english-grammar.com/past-simple-past-continuous-exercise-1.html
PRESENT PERFECT AND PAST SIMPLE
http://web2.uvcs.uvic.ca/elc/studyzone/410/grammar/ppvpast1.htm
http://www.ego4u.com/en/cram-up/grammar/simpas-preper/tests?test3
PAST PERFECT AND PAST SIMPLE
http://www.perfect-english-grammar.com/past-perfect-exercise-3.html
http://www.englishpage.com/verbpage/verbs11.htm
