Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach vu » sach va, sach tu, sach uu
vu nang » vuc nang, va nang, vu dang
cam duc » cam xuc, cao duc, pham duc
va danh » va dinh, va dan, va hanh
x hoi » xa hoi, o hoi, x ho
de va » de van, ke va, le va
te va » tu va
thiet » thieu

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach vu nang x hoi. ((hieu qua) OR (lieu va)) cam duc va danh ((de va) OR (te va)) thiet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach vu nang x hoi. ((hieu qua) or (lieu va)) cam duc va danh ((de va) OR (te va)) thiet~".
• Adding a wildcard symbol may retrieve word variants: toc sach vu nang x hoi. ((hieu qua) or (lieu va)) cam duc va danh ((de va) OR (te va)) thiet*.