Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
cua tre » cua te, cua triet, dua tren
va hanh » van hanh, va thanh, va danh
cam loc » cam lo
hieu va » lieu va, hieu qua
cuu tre » cau tren, cau treo
o lang » hoa lang, hoi lang
loc va » hoc va, luc va
v lang » va lang, _ lang, van lang
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: doc sach ((v lang) or (o lang)) xa hoi. hieu va cam loc va hanh vi ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ((v lang) OR (o lang)) xa hoi. hieu va cam loc va hanh vi ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ((v lang) or (o lang)) xa hoi. hieu va cam loc va hanh vi ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: doc sach ((v lang) or (o lang)) xa hoi. hieu va cam loc va hanh vi ((cua tre) OR (cuu tre))*.