Perhaps you should try some spelling variations:
mai hoi » mai khoi, dai hoi, lai hoi
hieu de » hieu ve, hieu he, hieu le
va hanh » van hanh, va thanh, va danh
cuu tre » cau tren, cau treo
cua tre » cua te, cua triet, dua tren
so sac » so sach, so dac
sac ky » cac ky, sai ky
ma hoi » xa hoi, ma hoa, me hoi
de dat » de dao
nuoc » quoc, duoc, ngoc

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

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