Perhaps you should try some spelling variations:
ban hanh » ban hang
hieu van » hieu va, thien van, lieu va
cuu tre » cau tren, cau treo
cua tre » cua te, cua triet, dua tren
duc ban » duc tan, duc van, dua ban
lam duc » lam duoc, pham duc, nam duoc
van lam » van nam
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
sac ky » cac ky, sai ky
tu sac » tu sach, tu cac, tu 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 sac ky ((nang ma) or (sang ma)) hoi. hieu van lam duc ban hanh vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky ((nang ma) OR (sang ma)) hoi. hieu van lam duc ban hanh vi ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: tu sac ky ((nang ma) or (sang ma)) hoi. hieu van lam duc ban hanh vi ((cua tre) or (cuu tre))*.