Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
nay thuc » nam thuc, day thuc, nhan thuc
hoc sach » hoc sinh, hoc cac, hoc anh
cay thuc » cay thuoc, can thuc, day thuc
vat cuu » vat cua
dan vat » dang vat, van vat, dan va
vat dan » va dan, van dan, vat ran
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
cuu tre » cua tre, cau tren, cau treo

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) or (hoc sach)) ky lang xa hoi. hieu va ((nay thuc) OR (cay thuc)) vat dan vat cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) ky lang xa hoi. hieu va ((nay thuc) OR (cay thuc)) vat dan vat cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc sach)) ky lang xa hoi. hieu va ((nay thuc) OR (cay thuc)) vat dan vat cuu tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) ky lang xa hoi. hieu va ((nay thuc) OR (cay thuc)) vat dan vat cuu tre*.