Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach vuc » sach duoc, sach nuoc, sach truc
vuc nang » cuc nang, vu nang, chuc nang
dan doi » dan hoi, dan toi, van doi
doi cua » dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
va cam » va cham, va cao, va cai
luc va » duc va, tuc va, loc va
va dan » ca dan, va dao, va dau
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 doi 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 doi 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 doi cua tre*.