Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
cau treo » cau theo, cau triet, cau trieu
cau tren » cu tren, dau tren, ca tren
hieu va » lieu va, hieu qua
thuc ca » thuc cua, thuc can, thuc cao
dan tai » van tai, dan thi, han tai
tang xa » trang xa, tang ma, lang xa
dan vai » dan va, dan vat, den vai
va nam » van nam, ha nam, va nay
y tang » ky tang, 6 tang, 7 tang

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 y tang xa hoi. hieu va nam thuc ca ((dan vai) or (dan tai)) ((cau treo) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y tang xa hoi. hieu va nam thuc ca ((dan vai) OR (dan tai)) ((cau treo) OR (cau tren)).
• Adding a wildcard symbol may retrieve word variants: toc sach y tang xa hoi. hieu va nam thuc ca ((dan vai) or (dan tai)) ((cau treo) or (cau tren))*.