Perhaps you should try some spelling variations:
va thanh » ban thanh, va tinh, le thanh
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
dan dai » dat dai, can dai, dan dat
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
loc va » hoc va, luc va
va dan » ca dan, va dao, va dau
cua cu » cua chu, cua cau, cua su
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: so sach ky nang o hoi. hieu ((va thanh) OR (gia thanh)) loc va dan dai ((cua tre) or (cua cu))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky nang o hoi. hieu ((va thanh) OR (gia thanh)) loc va dan dai ((cua tre) OR (cua cu)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky nang o hoi. hieu ((va thanh) OR (gia thanh)) loc va dan dai ((cua tre) or (cua cu))".
• Adding a wildcard symbol may retrieve word variants: so sach ky nang o hoi. hieu ((va thanh) OR (gia thanh)) loc va dan dai ((cua tre) or (cua cu))*.