Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
hanh vai » hanh vi, hanh va, hanh tai
van hanh » van thanh, ban hanh, van anh
te sach » toc sach
ky dang » ky nang, ky danh
dang xa » dang xay, lang xa, dang ha
cac tac » cac bac, cac dac, cac tai
sach ky » sac ky, sach y, sach ty
cac toc » cac toi, cac nuoc, cac thoi
vai va » mai va, dai va, hai va
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 sach ky dang xa hoi. hieu vien ((((cac tac) OR (cac toc))) or (dat nuoc)) van hanh vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky dang xa hoi. hieu vien ((((cac tac) OR (cac toc))) OR (dat nuoc)) van hanh vai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky dang xa hoi. hieu vien ((((cac tac) OR (cac toc))) or (dat nuoc)) van hanh vai va thiet".
• Adding a wildcard symbol may retrieve word variants: te sach ky dang xa hoi. hieu vien ((((cac tac) OR (cac toc))) or (dat nuoc)) van hanh vai va thiet*.