Perhaps you should try some spelling variations:
thanh phan » thanh pho, thanh san, thanh toan
hieu van » hieu va, thien van, lieu va
phan cua » nhan cua, than cua, phat cua
quoc ban » quoc bao, quoc lan, quoc quan
duoc ban » duc ban, buoc ban, duoc bat
su sach » so sach, vu sach
ty nang » ky nang, ty xang, ty hang
sach ty » sach y, sach tu, sach thu
cua tre » cua te, cuu tre, cua triet
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 ty nang ((x hoi) or (o hoi)). hieu van nam ((duoc ban) OR (quoc ban)) thanh phan cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty nang ((x hoi) OR (o hoi)). hieu van nam ((duoc ban) OR (quoc ban)) thanh phan cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty nang ((x hoi) or (o hoi)). hieu van nam ((duoc ban) OR (quoc ban)) thanh phan cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ty nang ((x hoi) or (o hoi)). hieu van nam ((duoc ban) OR (quoc ban)) thanh phan cua tre*.