Perhaps you should try some spelling variations:
hai treo » thai tren, tai tro, dai theo
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
dang hai » dang khai, hang hai, dung hai
su sach » so sach, vu sach
ly nang » ky nang, ly hang, ly vang
nang ma » tang ma, sang ma, nang cao
nam tuc » nam truc, nam tu, nam thuoc
sach ly » sach y, sach lo, sach ty
va dang » van dang, va nang, va lang
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 ma hoi. hieu van ((nam tuc) OR (nam thuc)) va dang hai ((hai treo) or (vai tro))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ly nang ma hoi. hieu van ((nam tuc) OR (nam thuc)) va dang hai ((hai treo) OR (vai tro)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ly nang ma hoi. hieu van ((nam tuc) OR (nam thuc)) va dang hai ((hai treo) or (vai tro))".
• Adding a wildcard symbol may retrieve word variants: su sach ly nang ma hoi. hieu van ((nam tuc) OR (nam thuc)) va dang hai ((hai treo) or (vai tro))*.