Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
hanh ki » hanh vi, hanh ky, hanh kien
luc van » luoc van, luu van, duc van
xuc van » duc van, vuc van, xuc ban
sach vu » sach va, sach tu, sach uu
tu sach » thu sach, su sach, te 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
va cam » va cham, va cac, va cao
ki su » ky su

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