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