Perhaps you should try some spelling variations:
chat triet » chet triet, phat trien, chat thien
thanh lay » thanh lap, thanh tay, thanh lam
thanh ly » thanh ky, thanh le, khanh ly
dua ban » dia ban, cua ban, qua ban
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
cao dua » cao duc, ca dua, cay dua
va cao » va cac, va co, va dao
co hoi » co hoc, co loi
o hoi » o hoc, o hai, 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 (co hoi)). hieu va cao dua ban ((thanh ly) OR (thanh lay)) chat triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (co hoi)). hieu va cao dua ban ((thanh ly) OR (thanh lay)) chat triet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoi) or (co hoi)). hieu va cao dua ban ((thanh ly) OR (thanh lay)) chat triet*".