Perhaps you should try some spelling variations:
hoang van » hang va
tang van » dang van, trong van, tang luan
thuc day » thuc dan, thuc vat
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
van cau » van dau, van hau, van chat
cua tre » cua te, cuu tre, cua triet
xac va » tac va, ac va, bac 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: su sach y ((hoang van) or (tang van)) hoi. hieu van cau ((xac va) or (thuc day)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y ((hoang van) OR (tang van)) hoi. hieu van cau ((xac va) OR (thuc day)) hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach y ((hoang van) or (tang van)) hoi. hieu van cau ((xac va) or (thuc day)) hanh vi cua tre*.