Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
su sach » so sach, vu sach
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
y lang » _ lang, tay lang, yen lang
o lang » hoa lang, hoi lang
hieu v » hieu va, hieu ve, hieu 2
v pham » vi pham, d pham

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

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