Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cau tren » cu tren, dau tren, ca tren
vu nang » vuc nang, va nang, vu dang
va danh » va dinh, va dan, va hanh
danh di » danh du, xanh di, danh dien
v nang » va nang, van nang, voi nang
luc va » duc va, tuc va, loc va
di cau » da cau, diem cau
va cam » va cham, va cac, va cao
va co » vo co

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