Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hieu » cao hieu
thuc day » thuc dan
vai cuu » vai cua
dan vai » dan va, dan tai, dan vat
cuu tre » cua tre, cau tren, cau treo
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
van hoe » van hoa, van hoc, van hien
ky lang » ky nang, ky dang, ky tang
va nam » van nam, ha nam, va nay

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ky lang ((van hoe) OR (van hieu)). hieu va nam ((thuc vat) or (thuc day)) dan vai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky lang ((van hoe) OR (van hieu)). hieu va nam ((thuc vat) OR (thuc day)) dan vai cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky lang ((van hoe) OR (van hieu)). hieu va nam ((thuc vat) or (thuc day)) dan vai cuu tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky lang ((van hoe) OR (van hieu)). hieu va nam ((thuc vat) or (thuc day)) dan vai cuu tre*.