Perhaps you should try some spelling variations:
chat triet » chet triet, phat trien, chat thien
thanh lam » thanh lap, hanh lam, thanh nam
van thanh » ban thanh, van tuan
lam chat » luan chat, cao chat, ly chat
hieu van » thien van, lieu va, hieu ve
hieu va » lieu va, hieu qua
duc van » duc va, duc tan, duc manh
cau duc » cao duc, cau luc, chu duc
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang ((o hoi) or (o hai)). ((hieu van) OR (hieu va)) cau duc van thanh lam chat triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (o hai)). ((hieu van) OR (hieu va)) cau duc van thanh lam chat triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoi) or (o hai)). ((hieu van) OR (hieu va)) cau duc van thanh lam chat triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) or (o hai)). ((hieu van) OR (hieu va)) cau duc van thanh lam chat triet*.