Perhaps you should try some spelling variations:
dai hoi » dai hoc, dai hai, dai moi
cua tre » cua te, cua triet, dua tren
va hanh » van hanh, va thanh, va danh
hieu va » lieu va, hieu qua
sach ly » sach y, sach lo, sach ty
vu sach » vu bach, su sach, vu khach
mai hoi » mai khoi, lai hoi, mai doi
cuu tre » cau tren, cau treo
cac tu » cac thu, cach tu, cac du
ly van » le van, ly va, ly von

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ly van ((mai hoi) or (dai hoi)). hieu va cac tu va hanh vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ly van ((mai hoi) OR (dai hoi)). hieu va cac tu va hanh vi ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: vu sach ly van ((mai hoi) or (dai hoi)). hieu va cac tu va hanh vi ((cua tre) or (cuu tre))*.