Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
dieu cua » dieu tra
van hanh » van thanh, ban hanh, van anh
nuoc van » nuoc va, nuoc san, luoc van
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
lai ky » sai ky, dai ky
te cua » tue cua, le cua, de cua
te lai » te tai, te bai
o hoc » co hoc, mo hoc, so hoc
o hoi » co hoi, o hai, o hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: te lai ky nang ((o hoi) OR (o hoc)). hieu vien cac nuoc van hanh ((dieu cua) or (te cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te lai ky nang ((o hoi) OR (o hoc)). hieu vien cac nuoc van hanh ((dieu cua) OR (te cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te lai ky nang ((o hoi) OR (o hoc)). hieu vien cac nuoc van hanh ((dieu cua) or (te cua)) tre".
• Adding a wildcard symbol may retrieve word variants: te lai ky nang ((o hoi) OR (o hoc)). hieu vien cac nuoc van hanh ((dieu cua) or (te cua)) tre*.