Perhaps you should try some spelling variations:
cac thuc » cach thuc, cac thu, can thuc
hieu van » hieu va, thien van, lieu va
co sach » bo sach, cuon sach, hoc sach
va danh » va dinh, va hanh, dia danh
van cac » van hac, van cau, van bac
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
cua tre » cua te, cuu tre, cua triet
va dan » ca dan, va dao, va dau
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: co sach y ((nang xa) or (nang ma)) hoi. hieu van cac thuc ((va danh) OR (va dan)) di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach y ((nang xa) OR (nang ma)) hoi. hieu van cac thuc ((va danh) OR (va dan)) di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "co sach y ((nang xa) or (nang ma)) hoi. hieu van cac thuc ((va danh) OR (va dan)) di cua tre".
• Adding a wildcard symbol may retrieve word variants: co sach y ((nang xa) or (nang ma)) hoi. hieu van cac thuc ((va danh) OR (va dan)) di cua tre*.