Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
thanh ve » hanh ve, thanh va, thanh vien
thanh de » hanh de, thanh do, thanh le
van pham » san pham, van phan, van phat
tu sach » thu sach, su sach, te sach
so sach » so sanh, bo sach, co sach
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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) or (so sach)) ky nang o hoi. hieu van pham duc va ((thanh de) OR (thanh ve)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (so sach)) ky nang o hoi. hieu van pham duc va ((thanh de) OR (thanh ve)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (so sach)) ky nang o hoi. hieu van pham duc va ((thanh de) OR (thanh ve)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (so sach)) ky nang o hoi. hieu van pham duc va ((thanh de) OR (thanh ve)) cua tre*.