Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
cua viet » ca viet, hoa viet, cua vat
nam thuc » nam thuoc, nam thu, nam tu
nang mai » nang ma, nang tai, lang mai
hanh vai » hanh vi, hanh va, hanh tai
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
sach ho » sach hoi, sach ha, sach lo
mai hoi » mai khoi, dai hoi, lai hoi
ho nang » thi nang, kha nang, cao nang

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 ho nang mai hoi. ((hieu quan) or (hieu qua)) ((nam thuc) or (am thuc)) va hanh vai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ho nang mai hoi. ((hieu quan) OR (hieu qua)) ((nam thuc) OR (am thuc)) va hanh vai cua viet.
• Adding a wildcard symbol may retrieve word variants: tu sach ho nang mai hoi. ((hieu quan) or (hieu qua)) ((nam thuc) or (am thuc)) va hanh vai cua viet*.