Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
thanh vi » hanh vi, thanh va, thanh ve
va thanh » gia thanh, ban thanh, va tinh
hieu van » hieu va, thien van, lieu va
van dau » van dao, phan dau
ly nang » ky nang, ly hang, ly vang
dau xua » dau cua, dao xuan, dau luan
vi cua » vai cua, di cua
xua va » xuat va, vua va, sua va
cua te » cua tu
5 hoi » o hoi

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) OR (doc sach)) ly nang ((5 hoi) or (xa hoi)). hieu van dau xua va thanh vi cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ly nang ((5 hoi) OR (xa hoi)). hieu van dau xua va thanh vi cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) ly nang ((5 hoi) or (xa hoi)). hieu van dau xua va thanh vi cua te".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) ly nang ((5 hoi) or (xa hoi)). hieu van dau xua va thanh vi cua te*.