Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
toc sach » hoc sach, doc sach, nuoc sach
thuc dan » thuc hanh, hoc dan, thuc vat
cuu tre » cau tren, cau treo
dan dan » dang dan, ban dan, dao dan
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
cua tre » cua te, cua triet, dua tren
dan va » doan va, dan ca, ban va
va am » va lam, va cam

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) or (thuoc sach)) ky lang xa hoi. hieu va am thuc dan dan va ((cuu tre) OR (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (thuoc sach)) ky lang xa hoi. hieu va am thuc dan dan va ((cuu tre) OR (cua tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (thuoc sach)) ky lang xa hoi. hieu va am thuc dan dan va ((cuu tre) OR (cua tre))".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (thuoc sach)) ky lang xa hoi. hieu va am thuc dan dan va ((cuu tre) OR (cua tre))*.