Perhaps you should try some spelling variations:
sach cay » sach cap, sach nay, sach vay
van hanh » van thanh, ban hanh, van anh
sach hay » sach han, sach ha, sach nay
voi dat » hoi dat, noi dat, voi dac
luc van » luoc van, luu van, duc van
cac luc » cau luc, coc luc, cac nuoc
mang xa » lang xa, mang may, dang xay
hieu va » lieu va, hieu qua
vi dat » vi dai, va dat, ve dat

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 cay) or (sach hay)) mang xa hoi. hieu va cac luc van hanh ((vi dat) OR (voi dat)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach cay) OR (sach hay)) mang xa hoi. hieu va cac luc van hanh ((vi dat) OR (voi dat)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach cay) or (sach hay)) mang xa hoi. hieu va cac luc van hanh ((vi dat) OR (voi dat)) tren".
• Adding a wildcard symbol may retrieve word variants: tu ((sach cay) or (sach hay)) mang xa hoi. hieu va cac luc van hanh ((vi dat) OR (voi dat)) tren*.