Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nang cai » nang cao, nang tai, nang cap
hanh tai » thanh tai, hang tai, han tai
sang tai » hang tai, sang tao, tang tai
tai cua » thai cua, tai cuc, tri cua
va hanh » van hanh, va thanh, va danh
su sach » so sach, vu sach
nam luc » nang luc, nhan luc, nam thuc
sach ky » sac ky, sach y, sach ty
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 ((nam luc) or (am thuc)) va hanh tai 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 ((nam luc) OR (am thuc)) va hanh tai cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang cai) or (sang tai)) hoi. hieu van ((nam luc) or (am thuc)) va hanh tai cua tre*.