Perhaps you should try some spelling variations:
danh dien » dinh dien, danh kien, danh lien
hieu van » hieu va, thien van, lieu va
hac thuc » hoc thuc, ha thuc, thach thuc
dien cau » diem cau, dien cac, dien cu
cau tren » cu tren, dau tren, ca tren
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
va danh » va dinh, va dan, va hanh

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 danh dien cau tren~.
• 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 danh dien cau tren.
• Adding a wildcard symbol may retrieve word variants: so sach y ((nang xa) or (nang ma)) hoi. hieu van hac thuc va danh dien cau tren*.