Perhaps you should try some spelling variations:
sach cay » sach cap, sach hay, sach nay
dau tren » dau tien, dat tren, dau tieng
tu sach » thu sach, su sach, te sach
mang xa » lang xa, dang xay, mang cua
hieu va » lieu va, hieu qua
xuc van » luc van, vuc van, xuc ban
duc van » duc va, duc tan, duc manh
va cau » van cau, va cac, va dau
vi dau » vi dai, va dau, bi dau

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach cay ((mang xa) or (mang may)) hoi. hieu va cau ((xuc van) OR (duc van)) hanh vi dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach cay ((mang xa) OR (mang may)) hoi. hieu va cau ((xuc van) OR (duc van)) hanh vi dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach cay ((mang xa) or (mang may)) hoi. hieu va cau ((xuc van) OR (duc van)) hanh vi dau tren".
• Adding a wildcard symbol may retrieve word variants: tu sach cay ((mang xa) or (mang may)) hoi. hieu va cau ((xuc van) OR (duc van)) hanh vi dau tren*.