Perhaps you should try some spelling variations:
phat duy » pham duy, phat huy, phan duy
ban hanh » ban hang
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
ty tang » tay tang, ty xang, ty hang
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
ma hoi » xa hoi, ma hoa, me hoi

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 ty tang ((ma hoi) or (mai hoi)). hieu va phat duy ((ban hanh) or (van ban)) nam cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty tang ((ma hoi) OR (mai hoi)). hieu va phat duy ((ban hanh) OR (van ban)) nam cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach ty tang ((ma hoi) or (mai hoi)). hieu va phat duy ((ban hanh) or (van ban)) nam cua tre*.