Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hac thuc » hoc thuc, ha thuc, thach thuc
dan kien » danh kien, van kien, dan vien
kien cuu » khien cua, khien cau, dien cuc
so sach » so sanh, bo sach, co sach
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
van hac » van hoc, van ha, van hai
thuc va » thuc vat, thuc dan, thuc day
cuu tre » cua tre, cau tren, cau treo
va dan » ca dan, va dao, va dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach y ((nang xa) or (nang ma)) hoi. hieu van hac thuc va dan kien cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y ((nang xa) OR (nang ma)) hoi. hieu van hac thuc va dan kien cuu tre.
• Adding a wildcard symbol may retrieve word variants: so sach y ((nang xa) or (nang ma)) hoi. hieu van hac thuc va dan kien cuu tre*.