Perhaps you should try some spelling variations:
pham duy » pham duc
van hanh » van thanh, ban hanh, van anh
cau tren » cu tren, dau tren, ca tren
vu sach » vu bach, su sach, vu khach
vang xa » lang xa, ang xa, dang xay
mang xa » lang xa, mang may, dang xay
hieu va » lieu va, hieu qua
va pham » van pham, va phat, va phap
duy van » duy vat, dung van
vi cau » va cau, ve cau, di cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach y ((vang xa) or (mang xa)) hoi. hieu va pham duy van hanh vi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach y ((vang xa) OR (mang xa)) hoi. hieu va pham duy van hanh vi cau tren.
• Adding a wildcard symbol may retrieve word variants: vu sach y ((vang xa) or (mang xa)) hoi. hieu va pham duy van hanh vi cau tren*.