Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
cau tren » cu tren, dau tren, ca tren
doc sach » hoc sach, nuoc sach, dac sac
va nang » van nang, da nang, cam nang
hieu va » lieu va, hieu qua
cam luc » cam xuc, cau luc
va danh » va dinh, va dan, va hanh
danh di » danh du, xanh di, danh dien
v nang » vu nang, van nang, voi nang
va cam » va cham, va cac, va cao
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) or (doc sach)) ((v nang) OR (va nang)) xa hoi. hieu va cam luc va danh di cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ((v nang) OR (va nang)) xa hoi. hieu va cam luc va danh di cau tren*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (doc sach)) ((v nang) OR (va nang)) xa hoi. hieu va cam luc va danh di cau tren*".