Perhaps you should try some spelling variations:
doc sach » hoc sach, nuoc sach, dac sac
toc sach » hoc sach, thuoc sach, nuoc sach
hieu ve » hieu va, hieu van
ve pham » vi pham, v pham, ve phan
va hanh » van hanh, va thanh, va danh
lai cua » dai cua, hai cua, thai cua
nang o » nang co, nang ho, nang ro
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: ((doc sach) or (toc sach)) ky nang o hoi. hieu ve pham duc va hanh ((lai cua) OR (lai chau)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((doc sach) OR (toc sach)) ky nang o hoi. hieu ve pham duc va hanh ((lai cua) OR (lai chau)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((doc sach) or (toc sach)) ky nang o hoi. hieu ve pham duc va hanh ((lai cua) OR (lai chau)) triet".
• Adding a wildcard symbol may retrieve word variants: ((doc sach) or (toc sach)) ky nang o hoi. hieu ve pham duc va hanh ((lai cua) OR (lai chau)) triet*.