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
sach hoi » sach doi, cach thoi, hoach hoi
hieu van » thien van, lieu va, hieu ve
nang mai » nang ma, nang tai, lang mai
sach moi » sach doi, bach mai, sach bai
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
hanh di » hanh vi, hanh de, hang di
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 hoi) or (sach moi)) nang mai hoi. ((hieu van) or (hieu va)) nam thuc dan hanh di cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach hoi) OR (sach moi)) nang mai hoi. ((hieu van) OR (hieu va)) nam thuc dan hanh di cua viet.
• Adding a wildcard symbol may retrieve word variants: tu ((sach hoi) or (sach moi)) nang mai hoi. ((hieu van) or (hieu va)) nam thuc dan hanh di cua viet*.