Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
van hanh » van thanh, ban hanh, van anh
mai hoi » mai khoi, dai hoi, lai hoi
hieu ve » hieu va, hieu van
cam tuc » cam xuc, cam tu, nam thuc
tuc van » thuc van, truc van, tuc va
hanh di » hanh vi, hanh de, hang di
ma hoi » xa hoi, ma hoa, me hoi
cam ky » cao ky
ve cam » ve cham, ve cac, va cam
di dau » doi dau, bi dau, di du

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((cam ky) OR (cac ky)) nang ((ma hoi) OR (mai hoi)). hieu ve cam tuc van hanh di dau tren~.
• Adding a wildcard symbol may retrieve word variants: tu ((cam ky) or (cac ky)) nang ((ma hoi) or (mai hoi)). hieu ve cam tuc van hanh di dau tren*.