Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
thuc dan » thuc hanh, hoc dan, thuc vat
thuc day » thuc vat
hieu va » hieu qua
sach ky » sac ky, sach y, sach ty
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
dan tai » van tai, dan thi, han tai
tai cuu » tai cuc, tai buu, tai cua
cuu tre » cua tre, cau tren, cau treo

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ky lang xa hoi. ((hieu va) OR (lieu va)) nay ((thuc dan) or (thuc day)) dan tai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky lang xa hoi. ((hieu va) OR (lieu va)) nay ((thuc dan) OR (thuc day)) dan tai cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ky lang xa hoi. ((hieu va) OR (lieu va)) nay ((thuc dan) or (thuc day)) dan tai cuu tre".
• Adding a wildcard symbol may retrieve word variants: doc sach ky lang xa hoi. ((hieu va) OR (lieu va)) nay ((thuc dan) or (thuc day)) dan tai cuu tre*.