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
tang xa » trang xa, tang ma, lang xa
thuc ca » thuc cua, thuc can, thuc cao
sach ky » sac ky, sach y, sach ty
dan vai » dan va, dan vat, den vai
dan tai » van tai, dan thi, han tai
ky tang » ky nang, ky dang, kho tang
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 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 ky tang xa hoi. hieu va nam thuc ca ((dan vai) OR (dan tai)) ((cau treo) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky 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 ky tang xa hoi. hieu va nam thuc ca ((dan vai) or (dan tai)) ((cau treo) OR (cau tren))*.