Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu ve » hieu va, hieu van
cac tuc » cac toc, cac tu, cac tac
lua tre » cua tre, luy tre, dua tren
y nang » ky nang, ly nang, v nang
ve cac » va cac, vien cac
tuc ca » tuc cac, tuc cua, tuc xa
ca dan » cac dan, ca dao
dan vi » doan vi, don vi, dan va
vi lua » vi luu
x hoi » xa hoi, x ho
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 y nang ((((x hoi) or (5 hoi))) or (o hoi)). hieu ve cac tuc ca dan vi lua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y nang ((((x hoi) OR (5 hoi))) OR (o hoi)). hieu ve cac tuc ca dan vi lua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach y nang ((((x hoi) or (5 hoi))) or (o hoi)). hieu ve cac tuc ca dan vi lua tre*.