Perhaps you should try some spelling variations:
phap lang » phap nang, phap tang, phap sang
phu lang » phu khang, phu luong, phu quang
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
doan vi » doan va, don vi, doan thi
cac thu » cach thuc, cac thoi
van cac » van hac, van cau, van bac
cua tre » cua te, cuu tre, cua triet
ha hoi » hoa hoi, ha noi, xa hoi
thu va » thuc va, thue va, tu va
dan va » doan va, dan ca, ban va

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ((phu lang) OR (phap lang)) ha hoi. hieu van cac thu va ((dan va) or (doan vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((phu lang) OR (phap lang)) ha hoi. hieu van cac thu va ((dan va) OR (doan vi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((phu lang) OR (phap lang)) ha hoi. hieu van cac thu va ((dan va) or (doan vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((phu lang) OR (phap lang)) ha hoi. hieu van cac thu va ((dan va) or (doan vi)) cua tre*.