Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
thanh ha » thanh hoa, thanh hai, nhanh ha
cam thuc » am thuc, nam thuc, can thuc
cam thu » nam thu, cac thu, ca thu
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
sach v » sach va, sach 2, sach vay
ma hoi » mai hoi, xa hoi, ma hoa
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 v) OR (sach y)) nang ma hoi. hieu van ((cam thuc) or (cam thu)) ban thanh ha cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach v) OR (sach y)) nang ma hoi. hieu van ((cam thuc) OR (cam thu)) ban thanh ha cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach v) OR (sach y)) nang ma hoi. hieu van ((cam thuc) or (cam thu)) ban thanh ha cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach v) OR (sach y)) nang ma hoi. hieu van ((cam thuc) or (cam thu)) ban thanh ha cua tre*.