Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
hanh hai » thanh hai, nhanh hai, hanh tai
hang hai » hoang hai, hang tai, thanh hai
nang xa » nang x, lang xa, nang ma
cac tac » cac toc, cac bac, cac dac
te sac » te sach, te cac, te san
sac ky » cac ky, sai ky
thiet » thieu

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 nang xa hoi. hieu vien ((cac tac) or (dat nuoc)) van ((hanh hai) OR (hang hai)) va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sac ky nang xa hoi. hieu vien ((cac tac) OR (dat nuoc)) van ((hanh hai) OR (hang hai)) va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sac ky nang xa hoi. hieu vien ((cac tac) or (dat nuoc)) van ((hanh hai) OR (hang hai)) va thiet".
• Adding a wildcard symbol may retrieve word variants: te sac ky nang xa hoi. hieu vien ((cac tac) or (dat nuoc)) van ((hanh hai) OR (hang hai)) va thiet*.