Perhaps you should try some spelling variations:
chet triet » chuyen triet, thuyet triet
thanh lam » thanh lap, hanh lam, thanh nam
lam chet » lam chat, la chet, lam chu
hieu van » hieu va, thien van, lieu va
van cao » van dao, van bao, van hao
duc ban » duc van, dua ban, duc man
tu sach » thu sach, su sach, te sach
y nang » ky nang, ly nang, v nang
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 y nang ((o hoi) OR (o hai)). hieu van cao ((duc ban) or (duc tan)) thanh lam chet triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((o hoi) OR (o hai)). hieu van cao ((duc ban) OR (duc tan)) thanh lam chet triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang ((o hoi) OR (o hai)). hieu van cao ((duc ban) or (duc tan)) thanh lam chet triet".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((o hoi) OR (o hai)). hieu van cao ((duc ban) or (duc tan)) thanh lam chet triet*.