Perhaps you should try some spelling variations:
vat thanh » dat thanh, gat thanh, tat thanh
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, nam thuc, can thuc
san cua » sang cua, ban cua, dan cua
cam thu » nam thu, cac thu, ca thu
tang ma » mang may, tang van
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)) tang ma hoi. hieu van ((cam thuc) OR (cam thu)) vat thanh san cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach v) OR (sach y)) tang ma hoi. hieu van ((cam thuc) OR (cam thu)) vat thanh san cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach v) or (sach y)) tang ma hoi. hieu van ((cam thuc) OR (cam thu)) vat thanh san cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach v) or (sach y)) tang ma hoi. hieu van ((cam thuc) OR (cam thu)) vat thanh san cua tre*.