Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
vat hanh » vat thanh, van hanh, va hanh
cau thuc » cau truc, cuu thuc, can thuc
cua tre » cua te, cua triet, dua tren
van cau » van dau, van hau, van chat
tu sach » thu sach, su sach, te sach
cuu tre » cau tren, cau treo
ty hang » ly hang, thi hang, thu hang
o hoi » co hoi, o hoc, o hai

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ((ty hang) OR (ty xang)) o hoi. hieu van cau thuc vat hanh vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ty hang) OR (ty xang)) o hoi. hieu van cau thuc vat hanh vi ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ty hang) OR (ty xang)) o hoi. hieu van cau thuc vat hanh vi ((cua tre) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ty hang) OR (ty xang)) o hoi. hieu van cau thuc vat hanh vi ((cua tre) or (cuu tre))*.