Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
cau treo » cau theo, cau triet, cau trieu
mai khoi » mai khoa, tai khoa, cac khoi
van hanh » van thanh, ban hanh, van anh
xuc van » duc van, luc van, vuc van
hieu va » lieu va, hieu qua
hai xuc » hai cuc, hai xu, chat xuc
su sac » su sach, su cac, su xac
sac ky » cac ky, sai ky
ma hoi » mai hoi, xa hoi, ma hoa
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 sac ky nang ((ma hoi) or (mai khoi)). hieu va hai xuc van hanh vi ((cau treo) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sac ky nang ((ma hoi) OR (mai khoi)). hieu va hai xuc van hanh vi ((cau treo) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sac ky nang ((ma hoi) or (mai khoi)). hieu va hai xuc van hanh vi ((cau treo) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: su sac ky nang ((ma hoi) or (mai khoi)). hieu va hai xuc van hanh vi ((cau treo) OR (cau tren))*.