Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
cua viet » ca viet, hoa viet, cua vat
hoi tang » hoi lang, hoc tang, hoi dang
dan hanh » dang hanh, dan khanh, dan thanh
tang ma » mang may, tang van
te sach » toc sach
nam hoc » nam moc, nam hoi, am hoc
tu sach » thu sach, su sach, tu cach
ma hoi » mai hoi, xa hoi, ma hoa
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (te sach)) hoi tang ma hoi. ((hieu quan) or (hieu qua)) nam hoc dan hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (te sach)) hoi tang ma hoi. ((hieu quan) OR (hieu qua)) nam hoc dan hanh vi cua viet.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (te sach)) hoi tang ma hoi. ((hieu quan) or (hieu qua)) nam hoc dan hanh vi cua viet*.