Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
danh vai » danh sai, danh va, doanh van
thuc day » thuc dan, thuc vat
vai cua » dai cua, hai cua, lai cua
thuc va » thuc vat, thuc dan
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, nang ma
tu nang » tru nang, tu nong, tu nano
va do » va dao, va doc, va co

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) OR (toc sach)) tu nang xa hoi. hieu va do ((thuc va) or (thuc day)) danh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) tu nang xa hoi. hieu va do ((thuc va) OR (thuc day)) danh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) tu nang xa hoi. hieu va do ((thuc va) or (thuc day)) danh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) tu nang xa hoi. hieu va do ((thuc va) or (thuc day)) danh vai cua tre*.