Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
nam thuc » nam thuoc, am thuc, nam thu
ky dang » ky nang, ky danh
ky lang » ky nang, ky tang, tay lang
hieu ha » hieu hoa, hieu va, hieu ca
thuc va » thuc vat, thuc dan, thuc day
vai cau » va cau, van cau, lai chau
vai cac » va cac, tai cac, voi cac
va dan » ca dan, va dao, va dau

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 ((ky lang) or (ky dang)) xa hoi. hieu ha nam thuc va dan ((vai cau) OR (vai cac)) treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ((ky lang) OR (ky dang)) xa hoi. hieu ha nam thuc va dan ((vai cau) OR (vai cac)) treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ((ky lang) or (ky dang)) xa hoi. hieu ha nam thuc va dan ((vai cau) OR (vai cac)) treo".
• Adding a wildcard symbol may retrieve word variants: hoc sach ((ky lang) or (ky dang)) xa hoi. hieu ha nam thuc va dan ((vai cau) OR (vai cac)) treo*.