Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
van hanh » van thanh, ban hanh, van anh
hanh tai » thanh tai, hang tai, han tai
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
cuc tre » duc tre, cua tre, cuu tre
sac ky » cac ky, sai ky
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: te ((sac ky) or (sach y)) nang o hoi. hieu vien cac duc van hanh tai cuc tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sac ky) OR (sach y)) nang o hoi. hieu vien cac duc van hanh tai cuc tre.
• Adding a wildcard symbol may retrieve word variants: te ((sac ky) or (sach y)) nang o hoi. hieu vien cac duc van hanh tai cuc tre*.