Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
thanh de » hanh de, thanh ve, thanh do
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
cac toc » cac toi, cac nuoc, cac thoi
toc gia » toc giay, tac gia, quoc gia
nang o » nang co, nang ho, nang ro
cua tu » cua tuc, cua su, cua cu
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. ((hieu van) OR (hieu va)) cac toc gia thanh de ((cua te) or (cua tu))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang o hoi. ((hieu van) OR (hieu va)) cac toc gia thanh de ((cua te) OR (cua tu)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang o hoi. ((hieu van) OR (hieu va)) cac toc gia thanh de ((cua te) or (cua tu))".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang o hoi. ((hieu van) OR (hieu va)) cac toc gia thanh de ((cua te) or (cua tu))*.