Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nam thu, nha thuoc
hieu van » hieu va, thien van, lieu va
thuoc va » thuc va, thuoc ma, thuong va
tinh va » trinh van, trinh vat, tinh gia
sach ty » sach y, sach tu, sach thu
tu sach » thu sach, su sach, te sach
nang xa » lang xa, nang ma, mang xa
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ty ((nang xa) or (nang x)) hoi. hieu van nam thuoc va ((tinh va) OR (tich va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((nang xa) OR (nang x)) hoi. hieu van nam thuoc va ((tinh va) OR (tich va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((nang xa) or (nang x)) hoi. hieu van nam thuoc va ((tinh va) OR (tich va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((nang xa) or (nang x)) hoi. hieu van nam thuoc va ((tinh va) OR (tich va)) cua tre*.