Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
cau tren » cu tren, dau tren, ca tren
hoc sach » hoc sinh, hoc cac, hoc anh
nang xa » nang x, lang xa, nang ma
va danh » va dinh, va dan, va hanh
danh di » danh du, xanh di, danh dien
v nang » va nang, vu nang, van nang
va dao » ca dao
luc va » duc va, tuc va, loc va
di cau » da cau, diem cau
va cao » va cac, va co, va bao

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