Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thuc day » thuc dan
vai cuu » vai cua
dan vai » dan va, dan tai, dan vat
cuu tre » cua tre, cau tren, cau treo
sach ky » sac ky, sach y, sach ty
hieu va » hieu qua
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho 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 ky tang xa hoi. ((hieu va) or (lieu va)) nam ((thuc day) OR (thuc vat)) dan vai cuu tre~.
• 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 day) OR (thuc vat)) dan vai cuu tre.
• 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 day) OR (thuc vat)) dan vai cuu tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky tang xa hoi. ((hieu va) or (lieu va)) nam ((thuc day) OR (thuc vat)) dan vai cuu tre*.