Perhaps you should try some spelling variations:
dang xay » dang van, van xay
dau luan » dan luan, dat luan, khau luan
van hanh » van thanh, ban hanh, van anh
dieu cua » dieu tra
tu sach » thu sach, su sach, te sach
lang xa » lang ha, lang van
qua dau » qua da, qua bau, qua dan
vi cua » vai cua, di cua

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 _ ((lang xa) OR (dang xay)) hoi. hieu qua dau luan van hanh ((vi cua) or (dieu cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach _ ((lang xa) OR (dang xay)) hoi. hieu qua dau luan van hanh ((vi cua) OR (dieu cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach _ ((lang xa) OR (dang xay)) hoi. hieu qua dau luan van hanh ((vi cua) or (dieu cua)) tre".
• Adding a wildcard symbol may retrieve word variants: tu sach _ ((lang xa) OR (dang xay)) hoi. hieu qua dau luan van hanh ((vi cua) or (dieu cua)) tre*.