Perhaps you should try some spelling variations:
nhan thuc » nhan luc, dan thuc, toan thuc
van nhan » van phan, van thanh, danh nhan
hieu van » hieu va, thien van, lieu va
cua tre » cua te, cua triet, dua tren
thuc va » thuc vat, thuc dan, thuc day
cuu tre » cau tren, cau treo
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
can ky » van ky, dan ky, ban ky
va don » va dong, va doc, va do
tu can » tu ban, tu cac, thu canh

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu can ky ((nang xa) or (nang ma)) hoi. hieu van nhan thuc va don vi ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu can ky ((nang xa) OR (nang ma)) hoi. hieu van nhan thuc va don vi ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu can ky ((nang xa) or (nang ma)) hoi. hieu van nhan thuc va don vi ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: tu can ky ((nang xa) or (nang ma)) hoi. hieu van nhan thuc va don vi ((cua tre) OR (cuu tre))*.