Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
hang dau » hang va, hang tai
day hang » dat hang, dai hang, day nang
thuc day » thuc dan, thuc vat
cac thuc » cach thuc, cac thu, can thuc
dau cua » dai cua, day cua, cau cua
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa

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