Perhaps you should try some spelling variations:
dang xay » dang van, van xay
van hanh » van thanh, ban hanh, van anh
dau tren » dau tien, dat tren, dau tieng
tu sach » thu sach, su sach, te sach
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
va cham » va chat, va tham
soc van » hoc van, oc van, sac van
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 y ((((nang ma) or (dang xay))) or (nang x)) hoi. hieu va cham soc van hanh vi dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((((nang ma) OR (dang xay))) OR (nang x)) hoi. hieu va cham soc van hanh vi dau tren.
• Adding a wildcard symbol may retrieve word variants: tu sach y ((((nang ma) or (dang xay))) or (nang x)) hoi. hieu va cham soc van hanh vi dau tren*.