Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
dan hanh » dang hanh, dan khanh, dan thanh
thuc dan » thuc hanh, hoc dan, thuc vat
nam thuc » nam thuoc, am thuc, nam thu
hieu van » thien van, lieu va, hieu ve
nang mai » nang tai, lang mai, nang cai
nang ma » tang ma, sang ma, nang cao
sach ho » sach hoi, sach ha, sach lo
hieu va » lieu va, hieu qua
tu sach » thu sach, su sach, te sach
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) OR (nang ma)) hoi. ((hieu van) or (hieu va)) nam thuc dan hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ho ((nang mai) OR (nang ma)) hoi. ((hieu van) OR (hieu va)) nam thuc dan hanh vi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ho ((nang mai) OR (nang ma)) hoi. ((hieu van) or (hieu va)) nam thuc dan hanh vi cua viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ho ((nang mai) OR (nang ma)) hoi. ((hieu van) or (hieu va)) nam thuc dan hanh vi cua viet*.