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
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
cac tuc » cac toc, cac tu, cac tac
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
lang xa » lang ha, dang xay, lang van
dang xa » dang xay, dang ha, dang va
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: tu sach ky ((dang xa) OR (lang xa)) hoi. hieu vien ((cac tuc) or (cac nuoc)) van hanh vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((dang xa) OR (lang xa)) hoi. hieu vien ((cac tuc) OR (cac nuoc)) van hanh vai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((dang xa) OR (lang xa)) hoi. hieu vien ((cac tuc) or (cac nuoc)) van hanh vai va thiet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((dang xa) OR (lang xa)) hoi. hieu vien ((cac tuc) or (cac nuoc)) van hanh vai va thiet*.