Perhaps you should try some spelling variations:
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
va hanh » van hanh, va thanh, va danh
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
va nam » van nam, va nay
xuc va » duc va, tuc va, luc va
di cua » dai cua, doi cua, de cua
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 ((o hoi) or (xa hoi)). lieu ((va nam) OR (ha nam)) xuc va hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((o hoi) OR (xa hoi)). lieu ((va nam) OR (ha nam)) xuc va hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((o hoi) or (xa hoi)). lieu ((va nam) OR (ha nam)) xuc va hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((o hoi) or (xa hoi)). lieu ((va nam) OR (ha nam)) xuc va hanh di cua tre*.