Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
dua tren » dung tren
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cua triet, cua thep
hanh di » hanh vi, hanh de, hang di
cac duc » cac du, cao duc, cac dac
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
cuu tre » cau tren, cau treo
sach v » sach va, sach y, sach 2
v lang » va lang, o lang, _ lang

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 v lang xa hoi. hieu va cac duc va hanh di ((((cua tre) OR (dua tren))) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach v lang xa hoi. hieu va cac duc va hanh di ((((cua tre) OR (dua tren))) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach v lang xa hoi. hieu va cac duc va hanh di ((((cua tre) OR (dua tren))) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: doc sach v lang xa hoi. hieu va cac duc va hanh di ((((cua tre) OR (dua tren))) or (cuu tre))*.