WHILE-WHEN

http://www.englishmedialab.com/GrammarGames/perfectpast/past%20progressive%20vs.%20past%20simple%20betting.html

http://www.englisch-hilfen.de/en/exercises/tenses/simple_past_progressive2.htm

http://www.englishpage.com/verbpage/pastcontinuous.html

http://www.englisch-hilfen.de/en/exercises/tenses/simple_past_progressive.htm

http://www.englishtenses.com/test/when_or_while_test

http://www.englishexercises.org/makeagame/viewgame.asp?id=734

http://www.eamus.it/exercises/verbs-past-simple-continuous.htm