Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
nang mai » nang ma, nang tai, lang mai
nam thuc » nam thuoc, am thuc, nam thu
vat hanh » vat thanh, van hanh, va hanh
cua viet » ca viet, hoa viet, cua vat
tu sach » thu sach, su sach, te sach
sach ho » sach hoi, sach ha, sach lo
ho nang » thi nang, kha nang, cao nang
mai hoi » mai khoi, dai hoi, lai hoi
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 ho nang mai hoi. ((hieu quan) or (hieu qua)) nam thuc vat hanh vi 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 vat hanh vi cua viet.
• Adding a wildcard symbol may retrieve word variants: tu sach ho nang mai hoi. ((hieu quan) or (hieu qua)) nam thuc vat hanh vi cua viet*.