Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
van hanh » van thanh, ban hanh, van anh
te sach » toc sach
sach ty » sach y, sach tu, sach thu
nang ro » nang co, nang ho, nang ra
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang x
cac co » cac cong
co van » cao van, vo van, so van
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: te sach ty ((nang o) or (nang ro)) hoi. ((hieu van) OR (hieu va)) cac co van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty ((nang o) OR (nang ro)) hoi. ((hieu van) OR (hieu va)) cac co van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty ((nang o) or (nang ro)) hoi. ((hieu van) OR (hieu va)) cac co van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: te sach ty ((nang o) or (nang ro)) hoi. ((hieu van) OR (hieu va)) cac co van hanh vi cua tre*.