Perhaps you should try some spelling variations:
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
truc va » thuc va, thuc vat, trung va
va hanh » van hanh, va thanh, va danh
sach 6 » sach y, sach 2
ve cau » ke cau, va cau, ve cac
vi su » va su, ki su, oi su
ve su » va su
tang » nang, dang, bang

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su sach 6 tang ((le hoi) or (ma hoa)). hieu ve cau truc va hanh ((vi su) OR (ve su)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach 6 tang ((le hoi) OR (ma hoa)). hieu ve cau truc va hanh ((vi su) OR (ve su)) viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach 6 tang ((le hoi) or (ma hoa)). hieu ve cau truc va hanh ((vi su) OR (ve su)) viet".
• Adding a wildcard symbol may retrieve word variants: su sach 6 tang ((le hoi) or (ma hoa)). hieu ve cau truc va hanh ((vi su) OR (ve su)) viet*.