Perhaps you should try some spelling variations:
hieu hien » bieu hien, dieu hien, chieu chien
hanh thai » nhanh thai, hinh thai, hanh tai
hieu vien » hieu viec, thieu nien, hieu tieng
thai cua » than cua, tai cuc, tri cua
van hanh » van thanh, ban hanh, van anh
nuoc van » nuoc va, nuoc san, luoc van
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
cua tre » cua te, cuu tre, cua triet
thu san » thuy san, thu ban, phu san
tu bac » tu ban, tu cac, tu bat
nang o » nang co, nang ho, nang ro
o lai » o lao

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu bac) or (thu san)) ky nang o lai. ((hieu vien) OR (hieu hien)) cac nuoc van hanh thai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu bac) OR (thu san)) ky nang o lai. ((hieu vien) OR (hieu hien)) cac nuoc van hanh thai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu bac) or (thu san)) ky nang o lai. ((hieu vien) OR (hieu hien)) cac nuoc van hanh thai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu bac) or (thu san)) ky nang o lai. ((hieu vien) OR (hieu hien)) cac nuoc van hanh thai cua tre*.