Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tran van » luan van
vat tran » vat ran, vat trong, vach tran
nam thuc » nam thuoc, am thuc, nam thu
cau treo » cau theo, cau tren, cau triet
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, mang xa
cuu tre » cua tre, cau tren
va nam » van nam, ha nam, va nay

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

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