Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
nang cai » nang cao, nang cap, nang can
hieu van » hieu va, thien van, lieu va
nang tai » hang tai, tang tai, sang tai
su sach » vu sach
tai cua » thai cua, tai cuc, tri cua
va hanh » van hanh, va thanh, va danh
cau luc » cau truc, cau phuc
van cau » van dau, van hau, van chat
so sach » so sanh, bo sach, co sach
cua tre » cua te, cuu tre, cua triet
luc va » duc va, tuc va, loc va

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) OR (so sach)) ty ((nang cai) or (nang tai)) hoi. hieu van cau luc va hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) ty ((nang cai) OR (nang tai)) hoi. hieu van cau luc va hanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) OR (so sach)) ty ((nang cai) or (nang tai)) hoi. hieu van cau luc va hanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sach) OR (so sach)) ty ((nang cai) or (nang tai)) hoi. hieu van cau luc va hanh tai cua tre*.