Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
cam thuc » am thuc, nam thuc, cam thu
thuc van » thuc vat, thuc dan, thuc va
tu nong » tu cong, tu tong, tu tuong
hanh di » hanh de, hang di, danh di
cuu tre » cua tre, cau tren, cau treo
va cam » va cham, va cac, va cao

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ((tu nong) OR (tu dong)) xa hoi. lieu va cam thuc van ((hanh di) or (hanh vi)) cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ((tu nong) OR (tu dong)) xa hoi. lieu va cam thuc van ((hanh di) OR (hanh vi)) cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ((tu nong) OR (tu dong)) xa hoi. lieu va cam thuc van ((hanh di) or (hanh vi)) cuu tre".
• Adding a wildcard symbol may retrieve word variants: hoc sach ((tu nong) OR (tu dong)) xa hoi. lieu va cam thuc van ((hanh di) or (hanh vi)) cuu tre*.