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

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 hoi. ((hieu ha) OR (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 hoi. ((hieu ha) OR (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 hoi. ((hieu ha) OR (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 hoi. ((hieu ha) OR (hieu va)) nam thuc vat tran van ((cuu tre) or (cau treo))*.