Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
va thanh » ban thanh, va tinh, le thanh
phat duc » pham duc, phan duc, phan duoc
van phat » va phat, van chat, van phan
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
de cua » le cua, te cua, dieu cua
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 phat duc ((va thanh) OR (gia 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. hieu van phat duc ((va thanh) OR (gia 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. hieu van phat duc ((va thanh) OR (gia thanh)) de cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (so sach)) ky nang o hoi. hieu van phat duc ((va thanh) OR (gia thanh)) de cua tre*.