U7 - Past tense exercises
http://www.myenglishpages.com/site_php_files/grammar-exercise-simple-past.php
http://www.perfect-english-grammar.com/past-simple-exercise-7.html
http://www.really-learn-english.com/simple-past-exercises.html
http://www.helpforenglish.cz/article/2013012401-cviceni-past-simple-minuly-prosty-cas
http://www.speakspeak.com/a/html/d3a10_resources_grammar_beginners_pastsimple_mixed1_cz.htm
http://www.speakspeak.com/a/html/d3a10_resources_grammar_beginners_pastsimple_mixed1_cz.htm
http://jirpa.cz/anglictina/aj-testc-past2.htm
http://www.englisch-hilfen.de/en/exercises/tenses/simple_past_mix.htm
http://www.perfect-english-grammar.com/past-simple-exercise-4.html
https://www.ego4u.com/en/cram-up/grammar/simple-past/exercises?03