Perhaps you should try some spelling variations:
kmay nong » may cong, may nang
may nong » may cong, may nang, mo nong
te sach » toc sach
hieu va » lieu va, hieu qua
cac tac » cac toc, cac bac, cac dac
van vat » van chat, nhan vat
vat cua » mat cua, bat cua, dat cua
cua tre » cua te, cuu tre, cua triet
tac va » tac da, tac xa, tuc va
o hoi » co hoi, o hoc, o hai

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 ((may nong) or (kmay nong)) o hoi. hieu va cac tac va van vat cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ((may nong) OR (kmay nong)) o hoi. hieu va cac tac va van vat cua tre.
• Adding a wildcard symbol may retrieve word variants: te sach ((may nong) or (kmay nong)) o hoi. hieu va cac tac va van vat cua tre*.