Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, va tinh
thanh ca » thanh cha, thanh cac, thanh ha
so sach » so sanh, bo sach, co sach
cao hoi » cau hoi, co hoi, cao hoc
duoc va » nuoc va, duc va, duoc ma
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, may nang
v nang » va nang, vu nang, van nang
va nam » van nam, va nay
ca cua » co cua

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 ((y nang) or (v nang)) cao hoi. hieu ((va nam) OR (ha nam)) duoc va thanh ca cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ((y nang) OR (v nang)) cao hoi. hieu ((va nam) OR (ha nam)) duoc va thanh ca cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ((y nang) or (v nang)) cao hoi. hieu ((va nam) OR (ha nam)) duoc va thanh ca cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ((y nang) or (v nang)) cao hoi. hieu ((va nam) OR (ha nam)) duoc va thanh ca cua tre*.