Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
thanh ha » thanh hoa, thanh hai, nhanh ha
thuc ban » thuoc ban, thuc dan, thu ban
cam thuc » am thuc, nam thuc, cam thu
hieu van » hieu va, thien van, lieu va
su sach » vu sach
van cam » van nam, van lam, van cau
cua tre » cua te, cuu tre, cua triet
sang ma » tang ma, sang tao, mang may
nang ma » tang ma, nang cao, mang may
so sach » so sanh, bo sach, co sach
ha cua » hoa cua, hai cua, nha cua

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) OR (so sach)) v ((nang ma) or (sang ma)) hoi. hieu van cam thuc ban thanh ha cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) v ((nang ma) OR (sang ma)) hoi. hieu van cam thuc ban thanh ha cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) OR (so sach)) v ((nang ma) or (sang ma)) hoi. hieu van cam thuc ban thanh ha cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sach) OR (so sach)) v ((nang ma) or (sang ma)) hoi. hieu van cam thuc ban thanh ha cua tre*.