Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
dien cuu » dien cuc, dien cu, dien cua
ban hanh » ban hang
cau duc » cao duc, cau luc, chu duc
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va
cuu tre » cua tre, cau tren, cau treo
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: toc sach ky nang o hoi. ((hieu ve) or (hieu van)) cau duc ((ban hanh) or (gia thanh)) dien cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang o hoi. ((hieu ve) OR (hieu van)) cau duc ((ban hanh) OR (gia thanh)) dien cuu tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang o hoi. ((hieu ve) or (hieu van)) cau duc ((ban hanh) or (gia thanh)) dien cuu tre*.