Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
vat hanh » vat thanh, van hanh, va hanh
cam thuc » am thuc, nam thuc, cam thu
cua tre » cua te, cua triet, dua tren
hanh di » hanh vi, hanh de, hang di
sach ky » sach y, sach ty, sach kem
van cam » van nam, van lam, van cau
cuu tre » cau tren, cau treo
nang ma » tang ma, sang ma, nang cao
ma hoi » mai hoi, xa hoi, ma hoa
sac ky » cac ky, sai ky

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 (sac ky)) nang ma hoi. hieu van cam thuc vat hanh di ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sac ky)) nang ma hoi. hieu van cam thuc vat hanh di ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) or (sac ky)) nang ma hoi. hieu van cam thuc vat hanh di ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) or (sac ky)) nang ma hoi. hieu van cam thuc vat hanh di ((cua tre) OR (cuu tre))*.