Perhaps you should try some spelling variations:
so sach » so sanh, bo sach, co sach
de xang » de dang, de tang, le xang
le dang » le tang, le dan, le quang
hieu va » lieu va, hieu qua
va giao » van giao, va giai, va gia
va hanh » van hanh, va thanh, va danh
vai va » dai va, hai va, lai va
thiet » thieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ((de xang) or (le dang)) xa hoi. hieu va giao duc va hanh ((vai va) OR (mai va)) thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ((de xang) OR (le dang)) xa hoi. hieu va giao duc va hanh ((vai va) OR (mai va)) thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ((de xang) or (le dang)) xa hoi. hieu va giao duc va hanh ((vai va) OR (mai va)) thiet".
• Adding a wildcard symbol may retrieve word variants: so sach ((de xang) or (le dang)) xa hoi. hieu va giao duc va hanh ((vai va) OR (mai va)) thiet*.