Perhaps you should try some spelling variations:
nang cai » nang cao, nang cap, nang can
nang tai » hang tai, tang tai, sang tai
hieu van » hieu va, thien van, lieu va
hanh tai » thanh tai, hang tai, han tai
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
van cau » van dau, van hau, van chat
cau luc » cau truc, cau phuc
va hanh » van hanh, va thanh, va danh
tai cua » thai cua, tai cuc, tri cua
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 ky ((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 ky ((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 ky ((nang cai) or (nang tai)) hoi. hieu van cau luc va hanh tai cua tre*.