Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
ly quang » le quang, vu quang
co sach » bo sach, cuon sach, hoc sach
cac tuc » cac toc, cac tu, cac nuoc
cac tac » cac toc, cac bac, cac dac
cuc tre » duc tre, cua tre, cuu tre
hieu ve » hieu va, hieu van

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

• Performing a fuzzy search may retrieve terms with similar spellings: co sach ((ly hang) or (ly quang)) xa hoi. hieu ve ((cac tuc) OR (cac tac)) van hanh tai cuc tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach ((ly hang) OR (ly quang)) xa hoi. hieu ve ((cac tuc) OR (cac tac)) van hanh tai cuc tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "co sach ((ly hang) or (ly quang)) xa hoi. hieu ve ((cac tuc) OR (cac tac)) van hanh tai cuc tre".
• Adding a wildcard symbol may retrieve word variants: co sach ((ly hang) or (ly quang)) xa hoi. hieu ve ((cac tuc) OR (cac tac)) van hanh tai cuc tre*.