Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
hieu cua » dieu cua, bieu cua, hieu ca
va thanh » gia thanh, ban thanh, va tinh
tai cua » thai cua, tai cuc, tri cua
ang xa » lang xa, mang xa, dang xay
cac lo » cac lop, cac co, cac bo
tai ca » tai cac, tai cao, bai ca
lo va » lo van, lao va, ly va

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach y ang xa hoi. ((hieu cua) OR (hieu qua)) cac lo va thanh ((tai ca) or (tai cua)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach y ang xa hoi. ((hieu cua) OR (hieu qua)) cac lo va thanh ((tai ca) OR (tai cua)) viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach y ang xa hoi. ((hieu cua) OR (hieu qua)) cac lo va thanh ((tai ca) or (tai cua)) viet".
• Adding a wildcard symbol may retrieve word variants: hoc sach y ang xa hoi. ((hieu cua) OR (hieu qua)) cac lo va thanh ((tai ca) or (tai cua)) viet*.