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 tren, cau triet
tang xa » trang xa, tang ma, lang xa
hieu va » hieu qua
sach ky » sac ky, sach y, sach ty
ky tang » ky nang, ky dang, kho tang
thuc ca » thuc cua, thuc can, thuc cao
dan vai » dan va, dan tai, dan vat

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) OR (lieu va)) nam thuc ca ((dan vai) or (tran thi)) cau treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky tang xa hoi. ((hieu va) OR (lieu va)) nam thuc ca ((dan vai) OR (tran thi)) cau treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky tang xa hoi. ((hieu va) OR (lieu va)) nam thuc ca ((dan vai) or (tran thi)) cau treo".
• Adding a wildcard symbol may retrieve word variants: toc sach ky tang xa hoi. ((hieu va) OR (lieu va)) nam thuc ca ((dan vai) or (tran thi)) cau treo*.