Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
sach vuc » sach duoc, sach nuoc, sach truc
vuc nang » cuc nang, vu nang, chuc nang
van hanh » van thanh, ban hanh, van anh
hanh ki » hanh vi, hanh ky, hanh kien
xuc van » duc van, luc van, vuc van
tu sach » thu sach, su sach, te sach
dai hoi » dai hoc, dai hai, dai moi
mai hoi » mai khoi, lai hoi, mai doi
va cao » va cac, va co, va dao
va cam » va cham, va cac, va cai
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 vuc nang ((mai hoi) OR (dai hoi)). hieu ((va cam) or (va cao)) xuc van hanh ki su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach vuc nang ((mai hoi) OR (dai hoi)). hieu ((va cam) OR (va cao)) xuc van hanh ki su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach vuc nang ((mai hoi) OR (dai hoi)). hieu ((va cam) or (va cao)) xuc van hanh ki su triet".
• Adding a wildcard symbol may retrieve word variants: tu sach vuc nang ((mai hoi) OR (dai hoi)). hieu ((va cam) or (va cao)) xuc van hanh ki su triet*.