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