Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
doc sach » hoc sach, toc sach, nuoc sach
hanh di » hanh vi, hanh de, hang di
va hanh » van hanh, va thanh, va danh
cac luc » cau luc, coc luc, cac nuoc
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
o lang » hoa lang, hoi lang
v lang » va lang, _ lang, van lang
luc va » duc va, tuc va, loc va
di cua » dai cua, doi cua, de cua

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

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