Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
so sach » so sanh, bo sach, co sach
danh vi » hanh vi, dinh vi, danh di
thuc va » thuc vat, thuc dan, thuc day
van cac » van hac, van cau, van bac
lang xa » lang ha, dang xay, lang van
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
tuc va » truc va, tuc xa, duc va
vi cua » vai cua, di cua

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 ((lang xa) or (nang ma)) hoi. hieu van cac ((tuc va) OR (thuc va)) danh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y ((lang xa) OR (nang ma)) hoi. hieu van cac ((tuc va) OR (thuc va)) danh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach y ((lang xa) or (nang ma)) hoi. hieu van cac ((tuc va) OR (thuc va)) danh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach y ((lang xa) or (nang ma)) hoi. hieu van cac ((tuc va) OR (thuc va)) danh vi cua tre*.