Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
sach kem » hanh kem
thuc van » thuc vat, thuc dan, thuc va
cam thuc » am thuc, nam thuc, cam thu
hieu van » hieu va, thien van, lieu va
hanh di » hanh vi, hanh de, hang di
van cam » van nam, van lam, van cau
cua tre » cua te, cuu tre, cua triet
sach ky » sach y, sach ty, sach hay
nang ma » tang ma, sang ma, nang cao
sac ky » cac ky, sai ky
di cua » dai cua, doi cua, de cua
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 ky) OR (sach kem))) or (sac ky)) nang ma hoi. hieu van cam thuc van hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((((sach ky) OR (sach kem))) OR (sac ky)) nang ma hoi. hieu van cam thuc van hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((((sach ky) OR (sach kem))) or (sac ky)) nang ma hoi. hieu van cam thuc van hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((((sach ky) OR (sach kem))) or (sac ky)) nang ma hoi. hieu van cam thuc van hanh di cua tre*.