Perhaps you should try some spelling variations:
dang xay » dang van
van hanh » van thanh, van anh, van ban
ban hanh » ban hang
co sach » bo sach, cuon sach, hoc sach
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
lam loc » lam duoc, lam ngoc
va lam » van lam, va lap
vi cua » vai cua, di cua
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: co sach ty ((dang xay) or (van xay)) hoi. hieu va lam loc ((van hanh) OR (ban hanh)) vi cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach ty ((dang xay) OR (van xay)) hoi. hieu va lam loc ((van hanh) OR (ban hanh)) vi cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "co sach ty ((dang xay) or (van xay)) hoi. hieu va lam loc ((van hanh) OR (ban hanh)) vi cua te".
• Adding a wildcard symbol may retrieve word variants: co sach ty ((dang xay) or (van xay)) hoi. hieu va lam loc ((van hanh) OR (ban hanh)) vi cua te*.