Perhaps you should try some spelling variations:
hai treo » thai tren, vai tro, tai tro
hieu van » hieu va, thien van, lieu va
khai hai » hai hai, khai thac, khai hoan
van dung » van dong, xay dung, tin dung
ly hang » ly quang
nam tuc » nam thuc, nam truc, nam tu
va dung » va duong, vat dung, va ung
ly nang » ky nang, ly vang, ly quang
su sach » so sach, vu sach
ma hoi » mai hoi, xa hoi, ma hoa

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 ((ly nang) OR (ly hang)) ma hoi. hieu van nam tuc ((va dung) or (van dung)) khai hai treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ly nang) OR (ly hang)) ma hoi. hieu van nam tuc ((va dung) OR (van dung)) khai hai treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ly nang) OR (ly hang)) ma hoi. hieu van nam tuc ((va dung) or (van dung)) khai hai treo".
• Adding a wildcard symbol may retrieve word variants: su sach ((ly nang) OR (ly hang)) ma hoi. hieu van nam tuc ((va dung) or (van dung)) khai hai treo*.