Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
vat hanh » vat thanh, van hanh, va hanh
can thuc » dan thuc, van thuc, cay thuc
cau thuc » cau truc, cuu thuc, cau phuc
hanh te » hanh tu, hanh ve, hanh de
tu sach » thu sach, su sach, te sach
tang ha » lang ha, tang ma, trung ha
ky tang » ky nang, ky dang, kho tang
so sach » so sanh, bo sach, co sach
cua tre » cua te, cuu tre, cua triet
te cua » tue cua, le cua, de cua

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

• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (so sach)) ky tang ha noi. hieu van ((cau thuc) OR (can thuc)) vat hanh te cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (so sach)) ky tang ha noi. hieu van ((cau thuc) OR (can thuc)) vat hanh te cua tre~".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (so sach)) ky tang ha noi. hieu van ((cau thuc) OR (can thuc)) vat hanh te cua tre*.