Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
chat duc » chat xuc, chat doc, chet duoc
cuu tre » cau tren, cau treo
sai kho » tai khoa, dai khoa, mai khoa
cua tre » cua te, cua triet, dua tren
duc van » duc va, duc tan, duc manh
va chat » van chat, va phat, cao chat
hieu va » lieu va, hieu qua
tang ma » mang may, tang van
dai kho » dai khoa, dai tho, dai ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu ((sai kho) or (dai kho)) tang ma hoa. hieu va chat duc van hanh vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sai kho) OR (dai kho)) tang ma hoa. hieu va chat duc van hanh vi ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: tu ((sai kho) or (dai kho)) tang ma hoa. hieu va chat duc van hanh vi ((cua tre) or (cuu tre))*.