Grammarly
Grammarly Handbook: Shifts in Writing
Five areas to edit for shifts in writing: Consistent Point of View, Consistent Verb Tenses, Verbs Consistent in Mood and Voice, Shifts from Indirect to Direct Questions/Quotations, and Shifts from British to American English. Each area...
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Indiana University of Pennsylvania: Writing Center: Shifty Tenses
Notes about verb tense, when it should and should not be changed, and what tense is best to use when writing about literature.
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H&h Publishing: Identify Inappropriate Shifts in Verb Tense
Practice improving four sentences by correct verb tense shifts and eliminating unnecessary words.