Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
sach thu » sach thue, sach thieu, sach tham
va triet » va thiet, va trien, ve triet
nang xa » nang x, lang xa, nang ma
hieu ve » hieu va, hieu van
cac duc » cao duc, cac dac, cac nuoc
va hanh » van hanh, va thanh, va danh
sac ky » cac ky, sai ky
tai va » thai va, mai va, tri va

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sach thu) or (sac ky)) nang xa hoi. hieu ve ((cac duc) OR (cac du)) va hanh tai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach thu) OR (sac ky)) nang xa hoi. hieu ve ((cac duc) OR (cac du)) va hanh tai va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach thu) or (sac ky)) nang xa hoi. hieu ve ((cac duc) OR (cac du)) va hanh tai va triet".
• Adding a wildcard symbol may retrieve word variants: thu ((sach thu) or (sac ky)) nang xa hoi. hieu ve ((cac duc) OR (cac du)) va hanh tai va triet*.