Perhaps you should try some spelling variations:
cac thuc » cach thuc, can thuc, cay thuc
so sach » so sanh, bo sach, co sach
nang ma » tang ma, sang ma, nang cao
cac thu » cach thuc, cac thoi
va danh » va dinh, va dan, va hanh
danh di » danh du, xanh di, danh dien
cua tre » cua te, cuu tre, cua triet
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: so sach y ((nang x) or (nang ma)) hoi. lieu va ((cac thuc) OR (cac thu)) va danh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y ((nang x) OR (nang ma)) hoi. lieu va ((cac thuc) OR (cac thu)) va danh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach y ((nang x) or (nang ma)) hoi. lieu va ((cac thuc) OR (cac thu)) va danh di cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach y ((nang x) or (nang ma)) hoi. lieu va ((cac thuc) OR (cac thu)) va danh di cua tre*.