Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
dan hanh » dang hanh, dan khanh, dan thanh
thuc dan » thuc hanh, hoc dan, thuc vat
can thuc » dan thuc, van thuc, cay thuc
sach tu » sach thu, cach tu, sach ty
cuu tre » cua tre, cau treo
hanh va » hang va, hanh vi
te sach » toc sach
tu nang » tru nang, tu nong, tu nano
hieu va » lieu va, hieu qua
va can » va chan, va cac, va cao
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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 tu nang ((x hoi) OR (o hoi)). hieu va can thuc dan hanh va ((cuu tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach tu nang ((x hoi) OR (o hoi)). hieu va can thuc dan hanh va ((cuu tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach tu nang ((x hoi) OR (o hoi)). hieu va can thuc dan hanh va ((cuu tre) or (cau tren))".
• Adding a wildcard symbol may retrieve word variants: te sach tu nang ((x hoi) OR (o hoi)). hieu va can thuc dan hanh va ((cuu tre) or (cau tren))*.