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https://www.englisch-hilfen.de/en/exercises_list/zeitformen.htm
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https://www.e-grammar.org/test-your-english/
https://www.ego4u.com/en/cram-up/grammar
http://usefulenglish.ru/grammar/tenses-exercise-ten
https://agendaweb.org/verbs/all-tenses.html
http://www.focus.olsztyn.pl/en-exercises-tenses.html
https://obrazovaka.ru/english/past-simple-past-
continuous-past-perfect.html
https://first-english.org/english_learning/english_tenses/comparison_tenses/a_english_tenses_comparison.htm#Past_Perfect
https://www.usingenglish.com/quizzes/
http://www.englishmaven.org/Pages/Verb%20Tenses.htm
https://www.englishpage.com/verbpage/verbtenseintro.html
https://www.perfect-english-grammar.com/grammar-exercises.html
https://www.englishexercises.org/