Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
toc sach » hoc sach, doc sach, thuoc sach
hoi sang » hoi lang, hoi dang, hoi nang
dan hanh » dang hanh, dan khanh, dan thanh
hanh di » hanh vi, hanh de, hang di
nam hoc » nam moc, nam hoi, am hoc
tu sach » thu sach, su sach, te sach
sang ma » tang ma, nang ma, sang tao
ma hoi » mai hoi, xa hoi, ma hoa
di cua » dai cua, doi cua, de 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 (toc sach)) hoi sang ma hoi. ((hieu quan) or (hieu qua)) nam hoc dan hanh di cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) hoi sang ma hoi. ((hieu quan) OR (hieu qua)) nam hoc dan hanh di cua vat.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) hoi sang ma hoi. ((hieu quan) or (hieu qua)) nam hoc dan hanh di cua vat*.