Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
toc sach » hoc sach, doc sach, nuoc sach
thanh do » thanh de, thanh pho, thanh hoa
dau tren » dau tien, dat tren, dau tieng
hang van » hoang van, hang va, dang van
van hoi » van hoa, van hoc, van hoe
hieu ve » hieu va, hieu van
cau duc » cau luc, chu duc, cau truc
cao duc » dao duc, cao suc, giao duc
y hang » ly hang, ty hang, yu hang
do dau » doi dau, do dai, mo dau

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 (thuoc sach)) y hang van hoi. hieu ve ((cau duc) or (cao duc)) gia thanh do dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (thuoc sach)) y hang van hoi. hieu ve ((cau duc) OR (cao duc)) gia thanh do dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (thuoc sach)) y hang van hoi. hieu ve ((cau duc) or (cao duc)) gia thanh do dau tren".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (thuoc sach)) y hang van hoi. hieu ve ((cau duc) or (cao duc)) gia thanh do dau tren*.