Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
tru nang » tra nang, tri nang, truc nano
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
nang xa » nang x, lang xa, nang ma
va cao » va cac, va co, va dao
tuc va » thuc va, truc va, duc va
vi cua » vai cua, di cua

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