Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
cau treo » cau theo, cau triet, cau trieu
hai luc » hai cuc, khai luoc, nhan luc
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
su hai » su tai
luc va » duc va, tuc va, loc va
hai ky » thai ky, hoi ky, hai ly
ma hoi » xa hoi, ma hoa, me hoi
va hai » van hai, va chai, va khai

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

• Performing a fuzzy search may retrieve terms with similar spellings: su hai ky nang ((ma hoi) or (mai hoi)). hieu va hai luc va hanh vi ((cau treo) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su hai ky nang ((ma hoi) OR (mai hoi)). hieu va hai luc va hanh vi ((cau treo) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su hai ky nang ((ma hoi) or (mai hoi)). hieu va hai luc va hanh vi ((cau treo) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: su hai ky nang ((ma hoi) or (mai hoi)). hieu va hai luc va hanh vi ((cau treo) OR (cau tren))*.