Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
cham duc » cham soc, pham duy, phan duc
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, nang cao
tai su » tai so, tai tu, lai su

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 y ((nang ma) or (nang x)) hoi. hieu ve ((cham duc) OR (pham duc)) van hanh tai su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((nang ma) OR (nang x)) hoi. hieu ve ((cham duc) OR (pham duc)) van hanh tai su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((nang ma) or (nang x)) hoi. hieu ve ((cham duc) OR (pham duc)) van hanh tai su triet".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((nang ma) or (nang x)) hoi. hieu ve ((cham duc) OR (pham duc)) van hanh tai su triet*.