Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
cua viet » ca viet, hoa viet, cua vat
lv nang » ly nang
van cam » van nam, van lam, van cau
hanh di » hanh vi, hanh de, hang di
v nang » va nang, vu nang, van nang
xuc va » tuc va, luc va, xac va
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 ((v nang) or (lv nang)) x hoi. hieu van cam ((xuc va) or (duc va)) hanh di cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((v nang) OR (lv nang)) x hoi. hieu van cam ((xuc va) OR (duc va)) hanh di cua viet.
• Adding a wildcard symbol may retrieve word variants: toc sach ((v nang) or (lv nang)) x hoi. hieu van cam ((xuc va) or (duc va)) hanh di cua viet*.