Perhaps you should try some spelling variations:
sach van » sach han, bach van, cach van
cau thuc » cau truc, cuu thuc, can thuc
thuc van » thuc vat, thuc dan, thuc va
van hanh » van thanh, ban hanh, van anh
sach va » sach xa, sach ha, sach dao
hieu ke » hieu kem, chieu ke, hieu ky
hanh de » hanh ve, hanh kem
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
ke cau » ket cau
de cua » le cua, te cua, dieu cua
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: su ((sach van) or (sach va)) nang o hoi. hieu ke cau thuc van hanh de cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach van) OR (sach va)) nang o hoi. hieu ke cau thuc van hanh de cua tre.
• Adding a wildcard symbol may retrieve word variants: su ((sach van) or (sach va)) nang o hoi. hieu ke cau thuc van hanh de cua tre*.