Perhaps you should try some spelling variations:
tan hanh » tan thanh, tang hanh, toan hanh
tham duc » pham duc, tham du, than duc
van tham » van thanh, van tuan, van chat
sach thu » sach thue, sach thieu, sach tham
hieu van » hieu va, thien van, lieu va
thu bang » thu ban, thu hang, chu bang
so sach » so sanh, bo sach, co sach
lai ve » loai ve, la ve, lai de
lai va » loai va, mai va, dai va
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach thu bang ((x hoi) or (o hoi)). hieu van tham duc tan hanh ((lai ve) OR (lai va)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach thu bang ((x hoi) OR (o hoi)). hieu van tham duc tan hanh ((lai ve) OR (lai va)) triet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach thu bang ((x hoi) or (o hoi)). hieu van tham duc tan hanh ((lai ve) OR (lai va)) triet*".