Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
vuc nang » cuc nang, vu nang, chuc nang
sach vuc » sach duoc, sach nuoc, sach truc
cua tre » cua te, cuu tre, cua triet
va cam » va cham, va cao, va cai
nang o » nang co, nang ho, nang ro
va dan » ca dan, va dau, va dap
va dao » ca dao
di cua » dai cua, doi cua, de cua
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 vuc nang o hoi. hieu ((va cam) or (va cac)) luc ((va dan) OR (va dao)) di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach vuc nang o hoi. hieu ((va cam) OR (va cac)) luc ((va dan) OR (va dao)) di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach vuc nang o hoi. hieu ((va cam) or (va cac)) luc ((va dan) OR (va dao)) di cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach vuc nang o hoi. hieu ((va cam) or (va cac)) luc ((va dan) OR (va dao)) di cua tre*.