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

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 ty nang xa hoi. ((hieu ha) or (hieu va)) nam thuc vat tran van ((cau tren) or (cau treo))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty nang xa hoi. ((hieu ha) OR (hieu va)) nam thuc vat tran van ((cau tren) OR (cau treo)).
• Adding a wildcard symbol may retrieve word variants: toc sach ty nang xa hoi. ((hieu ha) or (hieu va)) nam thuc vat tran van ((cau tren) or (cau treo))*.