Perhaps you should try some spelling variations:
vanh dai » van dai, vanh tai, van dao
nang ma » tang ma, sang ma, nang cao
lang xa » lang ha, dang xay, lang van
qua cac » cua cac
cac hoc » cach hoc, cac hop, bac hoc
hoc van » hoc dan, hoc va, hoc vat
te sac » te sach, te cac, te san
sac ky » cac ky, sai ky
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 sac ky ((nang ma) or (lang xa)) hoi. hieu qua cac hoc van ((vanh dai) OR (lanh dao)) cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sac ky ((nang ma) OR (lang xa)) hoi. hieu qua cac hoc van ((vanh dai) OR (lanh dao)) cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sac ky ((nang ma) or (lang xa)) hoi. hieu qua cac hoc van ((vanh dai) OR (lanh dao)) cua tu".
• Adding a wildcard symbol may retrieve word variants: te sac ky ((nang ma) or (lang xa)) hoi. hieu qua cac hoc van ((vanh dai) OR (lanh dao)) cua tu*.