Perhaps you should try some spelling variations:
sach tham » sach nha
tham nang » nham nang, tham lang, tham nhung
tang hanh » tang thanh, dang hanh, nang hanh
va triet » va thiet, va trien, ve triet
tan hanh » tan thanh, toan hanh, tran hanh
tham duc » pham duc, tham du, than duc
van tham » van thanh, van tuan, van chat
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
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: su sach tham nang ((x hoi) or (o hoi)). hieu van tham duc ((tan hanh) OR (tang hanh)) lai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach tham nang ((x hoi) OR (o hoi)). hieu van tham duc ((tan hanh) OR (tang hanh)) lai va triet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach tham nang ((x hoi) or (o hoi)). hieu van tham duc ((tan hanh) OR (tang hanh)) lai va triet*".