Perhaps you should try some spelling variations:
cac thuc » cach thuc, cac thu, can thuc
cau tren » cu tren, dau tren, ca tren
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
thuc va » thuc vat, thuc dan, thuc day
cuu tre » cua tre, cau treo
va cau » van cau, va dau, va cao

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 ky ((nang x) or (nang ma)) hoi. lieu va cac thuc va cau thi ((cuu tre) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang x) OR (nang ma)) hoi. lieu va cac thuc va cau thi ((cuu tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang x) or (nang ma)) hoi. lieu va cac thuc va cau thi ((cuu tre) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang x) or (nang ma)) hoi. lieu va cac thuc va cau thi ((cuu tre) OR (cau tren))*.