Perhaps you should try some spelling variations:
so sach » so sanh, bo sach, co sach
sach de » cach de, sach dao, sach dat
xang xa » lang xa, mang xa, dang xay
hieu va » lieu va, hieu qua
va giao » van giao, va giai, va gia
va hanh » van hanh, va thanh, va danh
ang xa » lang xa, mang xa, dang xay
vai va » mai va, dai va, lai va
hai va » hai van, thai va, hoi 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 xa) or (ang xa)) hoi. hieu va giao duc va hanh ((vai va) OR (hai va)) thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach de ((xang xa) OR (ang xa)) hoi. hieu va giao duc va hanh ((vai va) OR (hai va)) thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach de ((xang xa) or (ang xa)) hoi. hieu va giao duc va hanh ((vai va) OR (hai va)) thiet".
• Adding a wildcard symbol may retrieve word variants: so sach de ((xang xa) or (ang xa)) hoi. hieu va giao duc va hanh ((vai va) OR (hai va)) thiet*.