Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
luc van » luoc van, luu van, duc van
cam luc » cam xuc, cau luc
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va
lang ha » long ha
nang ma » tang ma, sang ma, nang cao
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: su sach y ((nang ma) or (lang ha)) hoi. ((hieu ve) OR (hieu van)) cam luc van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y ((nang ma) OR (lang ha)) hoi. ((hieu ve) OR (hieu van)) cam luc van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y ((nang ma) or (lang ha)) hoi. ((hieu ve) OR (hieu van)) cam luc van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach y ((nang ma) or (lang ha)) hoi. ((hieu ve) OR (hieu van)) cam luc van hanh vi cua tre*.