Perhaps you should try some spelling variations:
hanh vai » hanh vi, hanh va, hanh tai
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
qua cac » cua cac
duc van » duc tan, duc manh, duc phan
vai cua » dai cua, hai cua, lai cua
cua chu » sua chua
o hoi » co hoi, o hoc, o hai

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 ky nang ((xa hoi) or (o hoi)). hieu qua cac ((duc van) OR (duc va)) hanh vai cua chu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((xa hoi) OR (o hoi)). hieu qua cac ((duc van) OR (duc va)) hanh vai cua chu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((xa hoi) or (o hoi)). hieu qua cac ((duc van) OR (duc va)) hanh vai cua chu".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((xa hoi) or (o hoi)). hieu qua cac ((duc van) OR (duc va)) hanh vai cua chu*.