Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach vu » sach va, sach tu, sach uu
cua tre » cua te, cuu tre, cua triet
vu nang » vuc nang, va nang, vu dang
va cam » va cham, va cao, va cai
va dan » va dao, va dau, va dap
ca dan » cac dan, ca dao
di cua » dai cua, doi cua, de cua
x hoi » xa hoi, o hoi, x ho

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 vu nang x hoi. hieu ((va cam) or (va cac)) luc ((va dan) OR (ca dan)) di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach vu nang x hoi. hieu ((va cam) OR (va cac)) luc ((va dan) OR (ca dan)) di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach vu nang x hoi. hieu ((va cam) or (va cac)) luc ((va dan) OR (ca dan)) di cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach vu nang x hoi. hieu ((va cam) or (va cac)) luc ((va dan) OR (ca dan)) di cua tre*.