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

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