Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
sach cuc » sach cua, sach duoc, sach nuoc
cuc nang » chuc nang, cuu nang, cua 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
nang ma » tang ma, sang ma, nang cao
va cao » va cac, va co, va bao
va dao » ca dao
va cam » va cham, va cac, va cai
ma hoi » mai hoi, xa hoi, ma hoa
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 cuc nang ma hoi. hieu ((va cam) or (((va cao) or (va dao)))) xuc van hanh ki su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach cuc nang ma hoi. hieu ((va cam) OR (((va cao) OR (va dao)))) xuc van hanh ki su triet.
• Adding a wildcard symbol may retrieve word variants: tu sach cuc nang ma hoi. hieu ((va cam) or (((va cao) or (va dao)))) xuc van hanh ki su triet*.