Perhaps you should try some spelling variations:
nang cai » nang tai, nang cap, nang can
so sach » so sanh, bo sach, co sach
hieu va » lieu va, hieu qua
cau luc » cau truc, cau phuc
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
va cau » van cau, va cac, va dau
luc va » duc va, tuc va, loc va
vi cua » vai cua, di 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 cai) or (nang cao)) hoi. hieu va cau luc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y ((nang cai) OR (nang cao)) hoi. hieu va cau luc va hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: so sach y ((nang cai) or (nang cao)) hoi. hieu va cau luc va hanh vi cua tre*.