Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
hanh ki » hanh ky, hanh kien, thanh kim
luc van » luoc van, luu van, duc van
sach vu » sach va, sach tu, sach uu
su sach » so sach, vu sach
dai hoi » dai hoc, dai hai, dai moi
mai hoi » mai khoi, lai hoi, mai doi
vu nang » vuc nang, va nang, vu dang
hieu va » lieu va, hieu qua
co luc » coc luc, co luy
va co » vo co

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 vu nang ((mai hoi) OR (dai hoi)). hieu va co luc van ((hanh ki) or (hanh vi)) su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach vu nang ((mai hoi) OR (dai hoi)). hieu va co luc van ((hanh ki) OR (hanh vi)) su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach vu nang ((mai hoi) OR (dai hoi)). hieu va co luc van ((hanh ki) or (hanh vi)) su triet".
• Adding a wildcard symbol may retrieve word variants: su sach vu nang ((mai hoi) OR (dai hoi)). hieu va co luc van ((hanh ki) or (hanh vi)) su triet*.