... English Grammar Review! Copyright Hp Group (www.hp-vietnam.com) Trang 23 Please visit our website for more English study materials, including level A, B, C, TOEFL and IELTS 3. 3.1 Simple ... được dùng với 3 phó từ chỉ thời gian là: after, before và when. English Grammar Review! Copyright Hp Group (www.hp-vietnam.com) Trang 20 Please visit our website for more English study materials, ... theories on this subject have been proposed. English Grammar Review! Copyright Hp Group (www.hp-vietnam.com) Trang 19 Please visit our website for more English study materials, including level...