Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
van hanh » ban hanh, van anh, van ban
sach le » sach de, sach lo, sach kem
cach le » cach de, cac le, cach ben
xay hoi » xa hoi, tay hoi, cay phoi
hieu va » lieu va, hieu qua
va giao » van giao, va giai, va gia
vi va » vi van, vai va, vu 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: su ((sach le) or (cach le)) van xay hoi. hieu va giao duc ((van hanh) OR (van thanh)) vi va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach le) OR (cach le)) van xay hoi. hieu va giao duc ((van hanh) OR (van thanh)) vi va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach le) or (cach le)) van xay hoi. hieu va giao duc ((van hanh) OR (van thanh)) vi va thiet".
• Adding a wildcard symbol may retrieve word variants: su ((sach le) or (cach le)) van xay hoi. hieu va giao duc ((van hanh) OR (van thanh)) vi va thiet*.