Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
nang mai » nang ma, nang tai, lang mai
nam thuc » nam thuoc, am thuc, nam thu
sach hoi » sach moi, cach thoi, hoach hoi
hieu van » thien van, lieu va, hieu ve
sach doi » sach moi, sach dao, sach bai
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
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: su ((sach hoi) OR (sach doi)) nang mai hoi. ((hieu van) or (hieu va)) nam thuc va hanh di cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach hoi) OR (sach doi)) nang mai hoi. ((hieu van) OR (hieu va)) nam thuc va hanh di cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach hoi) OR (sach doi)) nang mai hoi. ((hieu van) or (hieu va)) nam thuc va hanh di cua viet".
• Adding a wildcard symbol may retrieve word variants: su ((sach hoi) OR (sach doi)) nang mai hoi. ((hieu van) or (hieu va)) nam thuc va hanh di cua viet*.