Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
cac thuc » cach thuc, cac thu, can thuc
thuc day » thuc dan, thuc vat
day hang » dat hang, dai hang, day nang
hang dau » hang va, hang tai
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
cua tre » cuu tre, cua triet, dua tren
y nang » ky nang, ly nang, v nang
cua te » cua tu

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 (hoc sach)) y nang xa hoi. hieu va cac thuc day hang dau ((cua tre) OR (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) y nang xa hoi. hieu va cac thuc day hang dau ((cua tre) OR (cua te)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc sach)) y nang xa hoi. hieu va cac thuc day hang dau ((cua tre) OR (cua te))".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) y nang xa hoi. hieu va cac thuc day hang dau ((cua tre) OR (cua te))*.