Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cam thuc » am thuc, nam thuc, cam thu
thuc van » thuc vat, thuc dan, thuc va
van hanh » van thanh, ban hanh, van anh
xang xa » lang xa, mang xa, ang xa
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
va cam » va cham, va cac, va cao
vi cua » vai cua, di cua

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ty xang xa hoi. hieu va cam thuc van hanh vi cua tre~".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ty xang xa hoi. hieu va cam thuc van hanh vi cua tre*.