Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
van hanh » van thanh, ban hanh, van anh
thu sach » thuat sach, thuoc sach, thu hoach
xuc van » duc van, luc van, vuc van
cau xuc » cam xuc, cau luc, cau truc
hieu va » lieu va, hieu qua
tu sach » su sach, te sach, tu cach
mang xa » lang xa, dang xay, mang cua
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) OR (thu sach)) cay ((mang xa) or (mang may)) hoi. hieu va cau xuc van hanh vi dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) cay ((mang xa) OR (mang may)) hoi. hieu va cau xuc van hanh vi dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) cay ((mang xa) or (mang may)) hoi. hieu va cau xuc van hanh vi dau tren".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) cay ((mang xa) or (mang may)) hoi. hieu va cau xuc van hanh vi dau tren*.