Perhaps you should try some spelling variations:
so triet » su triet, so thiet, bo triet
hanh hai » thanh hai, nhanh hai, hang hai
thuc van » thuc vat, thuc dan, thuc va
tuc van » truc van, tuc va, duc van
su sach » so sach, vu sach
qua cac » cua cac
y nang » ky nang, ly nang, v nang
so hai » son hai, su hai, so ha
hai so » dai so, tai so, thai son
o hoi » co hoi, o hoc, o hai

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 y nang ((o hoi) or (so hai)). hieu qua cac ((tuc van) OR (thuc van)) hanh hai so triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y nang ((o hoi) OR (so hai)). hieu qua cac ((tuc van) OR (thuc van)) hanh hai so triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y nang ((o hoi) or (so hai)). hieu qua cac ((tuc van) OR (thuc van)) hanh hai so triet".
• Adding a wildcard symbol may retrieve word variants: su sach y nang ((o hoi) or (so hai)). hieu qua cac ((tuc van) OR (thuc van)) hanh hai so triet*.