Perhaps you should try some spelling variations:
dau tieng » dau tien, cau tieng, day tieng
sach cay » sach cap, sach hay, sach nay
dau tren » dau tien, dat tren, dau trong
van hanh » van thanh, ban hanh, van anh
luc van » luoc van, luu van, duc van
cam luc » cam xuc, cau luc
tu sach » thu sach, su sach, te sach
mang xa » lang xa, dang xay, mang cua
hieu va » lieu va, hieu qua
va cam » va cham, va cac, va cao

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