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, nam thu, nam tu
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
va hanh » van hanh, va thanh, va danh
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) OR (am thuc)) va hanh vi cua viet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ho nang mai hoi. ((hieu quan) OR (hieu qua)) ((nam thuc) OR (am thuc)) va 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) OR (am thuc)) va hanh vi cua viet*.