Perhaps you should try some spelling variations:
doc sach » hoc sach, nuoc sach, dac sac
toc sach » hoc sach, thuoc sach, nuoc sach
thuc day » thuc dan, thuc vat
vai cuu » vai cua
dan vai » dan va, dan tai, dan vat
thuc va » thuc vat, thuc dan
cuu tre » cua tre, cau tren, cau treo
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
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: ((doc sach) OR (toc sach)) ky lang xa hoi. hieu va nam ((thuc va) or (thuc day)) dan vai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((doc sach) OR (toc sach)) ky lang xa hoi. hieu va nam ((thuc va) OR (thuc day)) dan vai cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((doc sach) OR (toc sach)) ky lang xa hoi. hieu va nam ((thuc va) or (thuc day)) dan vai cuu tre".
• Adding a wildcard symbol may retrieve word variants: ((doc sach) OR (toc sach)) ky lang xa hoi. hieu va nam ((thuc va) or (thuc day)) dan vai cuu tre*.