Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
nay thuc » nam thuc, cay thuc, day thuc
vai cuu » vai cua
dau vai » dau va, dau hai, dau tai
thuc va » thuc vat, thuc dan, thuc day
cuu tre » cua tre, cau tren, cau treo
hieu va » hieu qua
dang xa » dang xay, lang xa, dang ha
ky dang » ky nang, ky danh
va dau » va dao

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