Perhaps you should try some spelling variations:
day thanh » dao thanh, dat thanh, da thanh
cam thuc » am thuc, nam thuc, cam thu
thanh va » thanh van, hanh va, thanh ha
thuc day » thuc dan, thuc vat
hieu van » hieu va, thien van, lieu va
su sach » vu sach
cuu tre » cau tren, cau treo
van cam » van nam, van lam, van cau
nang ma » tang ma, sang ma, nang cao
so sach » so sanh, bo sach, co sach
cua tre » cua te, cua triet, dua tren

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: ((su sach) OR (so sach)) ky nang ma hoa. hieu van cam thuc day thanh va ((cuu tre) OR (cua tre))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (so sach)) ky nang ma hoa. hieu van cam thuc day thanh va ((cuu tre) OR (cua tre))~".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (so sach)) ky nang ma hoa. hieu van cam thuc day thanh va ((cuu tre) OR (cua tre))*.