Confusing Words:Practice Exercises
www.proprofs.com/quiz-school/story.php?title=commonly-confused-words-practice-1
highered.mheducation.com/sites/0073123587/student_view0/chapter5/commonly_confused_words_multiple-choice_exercise__extra_practice__group_2.html
http://www.mhhe.com/socscience/english/langan/sentence_skills/exercises/ch29/p4exr.htm
http://www.grammar-quizzes.com/confusedsum.html
spcollege.libguides.com/c.php?g=254288&p=1695265
www.englisch-hilfen.de/en/exercises_list/mix_words.htm