Perhaps you should try some spelling variations:
cac thuc » cach thuc, can thuc, cay thuc
so sach » so sanh, bo sach, co sach
cac thu » cach thuc, cac thoi
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, cua triet
hieu va » hieu qua
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
ma hoi » mai hoi, xa hoi, ma hoa
va dan » ca dan, va dao, va dau
dan di » danh di, dan da, dan de
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 ky tang ma hoi. ((hieu va) or (lieu va)) ((cac thuc) OR (cac thu)) va dan di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky tang ma hoi. ((hieu va) OR (lieu va)) ((cac thuc) OR (cac thu)) va dan di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky tang ma hoi. ((hieu va) or (lieu va)) ((cac thuc) OR (cac thu)) va dan di cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ky tang ma hoi. ((hieu va) or (lieu va)) ((cac thuc) OR (cac thu)) va dan di cua tre*.