Perhaps you should try some spelling variations:
danh tai » doanh tai, dinh tai, hanh tai
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, nam thuc, cam thu
tu sach » thu sach, su sach, te sach
cua tre » cua te, cua triet, dua tren
duc tre » duoc tren, duc tien
thuc va » thuc vat, thuc dan, thuc day
va danh » va dinh, va dan, va hanh
van cam » van nam, van lam, van cau
cuu tre » cau tren, cau treo
y nang » ky nang, ly nang, v nang
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang o hoi. hieu van cam thuc va danh tai ((duc tre) OR (((cua tre) OR (cuu tre))))~.
• Adding a wildcard symbol may retrieve word variants: tu sach y nang o hoi. hieu van cam thuc va danh tai ((duc tre) or (((cua tre) or (cuu tre))))*.