Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
sach cay » sach hay, sach nay, sach vay
van hanh » van thanh, ban hanh, van anh
truc van » truc va, thuc van, truc ban
sach cap » sach dao, sach bai, sach xa
hieu va » lieu va, hieu qua
mang xa » lang xa, dang xay, mang cua
va cau » van cau, va cac, va dau
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: te ((sach cay) OR (sach cap)) ((mang xa) or (mang may)) hoi. hieu va cau truc van hanh vi dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach cay) OR (sach cap)) ((mang xa) OR (mang may)) hoi. hieu va cau truc van hanh vi dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach cay) OR (sach cap)) ((mang xa) or (mang may)) hoi. hieu va cau truc van hanh vi dau tren".
• Adding a wildcard symbol may retrieve word variants: te ((sach cay) OR (sach cap)) ((mang xa) or (mang may)) hoi. hieu va cau truc van hanh vi dau tren*.