Perhaps you should try some spelling variations:
vat thanh » dat thanh, gat thanh, tat thanh
thanh hai » thanh phan, thanh hoa, thanh san
hieu van » hieu va, thien van, lieu va
cam thuc » nam thuc, cam thu, can thuc
nang ma » tang ma, sang ma, nang cao
hai cua » thai cua, dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
sach v » sach va, sach 2, sach vay
ma hoi » mai hoi, xa hoi, ma hoa

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 (am thuc)) vat thanh hai 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 (am thuc)) vat thanh hai 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 (am thuc)) vat thanh hai cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach v) or (sach y)) nang ma hoi. hieu van ((cam thuc) OR (am thuc)) vat thanh hai cua tre*.