Perhaps you should try some spelling variations:
nang cau » nang cao, hang cau, nang dau
hieu van » hieu va, thien van, lieu va
sach ty » sach y, sach tu, sach thu
van cac » van hac, van cau, van bac
thuc va » thuc dan, thuc day
dinh di » dinh du, dinh vi, danh di
cuu tre » cua tre, cau tren, cau treo
di cuu » di cau, di cua, dinh cuu

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sach ty) or (cac ky)) nang cau hoi. hieu van cac ((thuc va) OR (thuc vat)) dinh di cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach ty) OR (cac ky)) nang cau hoi. hieu van cac ((thuc va) OR (thuc vat)) dinh di cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach ty) or (cac ky)) nang cau hoi. hieu van cac ((thuc va) OR (thuc vat)) dinh di cuu tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach ty) or (cac ky)) nang cau hoi. hieu van cac ((thuc va) OR (thuc vat)) dinh di cuu tre*.