Perhaps you should try some spelling variations:
khanh vinh » thanh vinh, khanh linh, thanh binh
hanh vinh » thanh vinh, hanh tinh, anh vinh
cau tren » cu tren, dau tren, ca tren
cao duc » dao duc, cao suc, giao duc
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
ve cao » va cao, ve bao, ve cac
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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 ((x hoi) OR (o hoi)). hieu ve cao duc va ((hanh vinh) or (khanh vinh)) cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((x hoi) OR (o hoi)). hieu ve cao duc va ((hanh vinh) OR (khanh vinh)) cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((x hoi) OR (o hoi)). hieu ve cao duc va ((hanh vinh) or (khanh vinh)) cau tren".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((x hoi) OR (o hoi)). hieu ve cao duc va ((hanh vinh) or (khanh vinh)) cau tren*.