Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cau tren » cu tren, dau tren, ca tren
va nang » van nang, da nang, cam nang
hieu va » lieu va, hieu qua
cac luc » cau luc, coc luc, cac nuoc
va danh » va dinh, va dan, va hanh
danh di » danh du, xanh di, danh dien
v nang » vu nang, van nang, voi nang
luc va » duc va, tuc va, loc va
di cau » da cau, diem cau

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 (va nang)) xa hoi. hieu va cac luc va danh di cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((v nang) OR (va nang)) xa hoi. hieu va cac luc va danh di cau tren.
• Adding a wildcard symbol may retrieve word variants: toc sach ((v nang) or (va nang)) xa hoi. hieu va cac luc va danh di cau tren*.