Perhaps you should try some spelling variations:
ve triet » va trien, su triet
ban hanh » ban hang
hanh ve » hanh vi, hanh va, hanh kem
cac dac » cac dan, cac dai, cac bac
cac duc » cac du, cao duc, cac nuoc
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
sach 2 » sach y
2 nang » v nang
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi
ve ve » de ve, va ve, ke ve

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 2 nang ((x hoi) or (o hoi)). hieu ve ((cac duc) OR (cac dac)) ban hanh ve ve triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach 2 nang ((x hoi) OR (o hoi)). hieu ve ((cac duc) OR (cac dac)) ban hanh ve ve triet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach 2 nang ((x hoi) or (o hoi)). hieu ve ((cac duc) OR (cac dac)) ban hanh ve ve triet*".