Perhaps you should try some spelling variations:
sach vay » sach va, sach hay, sach nay
cua tre » cua te, cua triet, dua tren
hanh di » hanh vi, hanh de, hang di
va hanh » van hanh, va thanh, va danh
cac duc » cac du, cao duc, cac dac
hieu va » lieu va, hieu qua
cuu tre » cau tren, cau treo
lang xa » lang ha, dang xay, lang van
sach 2 » sach y

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc ((sach vay) or (sach 2)) lang xa hoi. hieu va cac duc va hanh di ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((sach vay) OR (sach 2)) lang xa hoi. hieu va cac duc va hanh di ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: doc ((sach vay) or (sach 2)) lang xa hoi. hieu va cac duc va hanh di ((cua tre) or (cuu tre))*.