Perhaps you should try some spelling variations:
sach tham » sach nha
toc sach » hoc sach, doc sach, thuoc sach
hanh vai » hanh va, hanh tai, hanh van
cac truc » cau truc, cac tru, cac trung
truc va » thuc va, thuc vat, trung va
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
cua tre » cua te, cuu tre, cua triet

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 tham ((nang xa) or (nang ma)) hoi. hieu va cac truc va ((hanh vai) or (hanh vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach tham ((nang xa) OR (nang ma)) hoi. hieu va cac truc va ((hanh vai) OR (hanh vi)) cua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach tham ((nang xa) or (nang ma)) hoi. hieu va cac truc va ((hanh vai) or (hanh vi)) cua tre*.