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College Board AP World History page
College Board AP European History page
Optional: WHAP review books
For sophomores who test this year (but also freshman if you want to get a start on it) there are multiple review books that are put out each year. Do not feel obligated to get one, but if it will help you to have a separate book to follow along with that hits the highlights and has practice questions, here are 2 good options:
Perfection Learning AMSCO info & McGraw Hill AP 5 steps to a 5 info (new versions are released each year)