Perhaps you should try some spelling variations:
nang mai » nang ma, nang tai, lang mai
cua tre » cua te, cuu tre, cua triet
va hanh » van hanh, va thanh, va danh
cac toc » cac toi, cac nuoc, cac thoi
cac loc » cac lop, cac hoc, cac nuoc
hieu va » lieu va, hieu qua
mai hoi » mai khoi, dai hoi, lai hoi
tu ban » thu ban, te ban
vi cua » vai cua, di cua
tu san » thu san, tu can, vu san

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu san) or (tu ban)) ky nang mai hoi. hieu va ((cac loc) OR (cac toc)) va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu san) OR (tu ban)) ky nang mai hoi. hieu va ((cac loc) OR (cac toc)) va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu san) or (tu ban)) ky nang mai hoi. hieu va ((cac loc) OR (cac toc)) va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu san) or (tu ban)) ky nang mai hoi. hieu va ((cac loc) OR (cac toc)) va hanh vi cua tre*.