Perhaps you should try some spelling variations:
hac thuc » hoc thuc, ha thuc, thach thuc
hieu van » hieu va, thien van, lieu va
cuu tre » cau tren, cau treo
cua tre » cua te, cua triet, dua tren
thuc va » thuc vat, thuc dan, thuc day
van hac » van hoc, van ha, van hai
nang xa » lang xa, nang ma, mang xa
sai ky » sac ky
va don » va dong, va doc, va do
su sai » su tai, su hai, su dai

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sai ky ((nang xa) or (nang x)) hoi. hieu van hac thuc va don vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sai ky ((nang xa) OR (nang x)) hoi. hieu van hac thuc va don vi ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: su sai ky ((nang xa) or (nang x)) hoi. hieu van hac thuc va don vi ((cua tre) or (cuu tre))*.