Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
sach ky » sac ky, sach ty, sach kem
cac dai » cac dan, cac bai, can dai
cac dac » cac dan, cac bac, cac tac
cuc tre » duc tre, cua tre, cuu tre
hieu ve » hieu va, hieu van
nang o » nang co, nang ho, nang ro
o hai » co hai, so hai, o lai

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) or (sach y)) nang o hai. hieu ve ((cac dac) OR (cac dai)) van hanh tai cuc tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach ky) OR (sach y)) nang o hai. hieu ve ((cac dac) OR (cac dai)) van hanh tai cuc tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach ky) or (sach y)) nang o hai. hieu ve ((cac dac) OR (cac dai)) van hanh tai cuc tre*".