Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
sach tu » sach thu, sach ty, sach uu
cach tu » cach thuc
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
cac duc » cac du, cao duc, cac dac
va hanh » van hanh, va thanh, va danh
ma hoi » mai hoi, xa hoi, ma hoa
vi cua » vai cua, di cua
cua tu » cua tuc, cua su, cua cu

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

• Performing a fuzzy search may retrieve terms with similar spellings: te ((sach tu) or (cach tu)) nang ma hoi. ((hieu van) OR (hieu va)) cac duc va hanh vi cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach tu) OR (cach tu)) nang ma hoi. ((hieu van) OR (hieu va)) cac duc va hanh vi cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach tu) or (cach tu)) nang ma hoi. ((hieu van) OR (hieu va)) cac duc va hanh vi cua tu".
• Adding a wildcard symbol may retrieve word variants: te ((sach tu) or (cach tu)) nang ma hoi. ((hieu van) OR (hieu va)) cac duc va hanh vi cua tu*.