Perhaps you should try some spelling variations:
nang cai » nang cao, nang tai, nang cap
sang tai » hang tai, sang tao, tang tai
hieu van » hieu va, thien van, lieu va
hanh tri » thanh tri, hanh tai, hanh trinh
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet

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 (sang tai)) hoi. hieu van ((nang luc) or (am thuc)) va hanh tri cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang cai) OR (sang tai)) hoi. hieu van ((nang luc) OR (am thuc)) va hanh tri cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang cai) or (sang tai)) hoi. hieu van ((nang luc) or (am thuc)) va hanh tri cua tre*.