Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, va tinh
hieu va » lieu va, hieu qua
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va danh, ban hanh
cua tre » cua te, cuu tre, cua triet
dang ma » dang mau, dang mam, dang mat
ky dang » ky nang, ky danh
ma hoi » mai hoi, xa hoi, ma hoa
tu ban » thu ban, te ban
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 dang ma hoi. hieu va cac hop ((va hanh) OR (va thanh)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu san) OR (tu ban)) ky dang ma hoi. hieu va cac hop ((va hanh) OR (va thanh)) vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu san) or (tu ban)) ky dang ma hoi. hieu va cac hop ((va hanh) OR (va thanh)) vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu san) or (tu ban)) ky dang ma hoi. hieu va cac hop ((va hanh) OR (va thanh)) vai cua tre*.