Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nha thuoc, cay thuoc
hieu van » hieu va, thien van, lieu va
tinh va » tich va, trinh van, trinh vat
va tinh » may tinh
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
va cua » va chua, via cua, ca cua

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) OR (nam thu)) va tinh 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) OR (nam thu)) va tinh 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) OR (nam thu)) va tinh va cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((nang xa) or (nang x)) hoi. hieu van ((nam thuoc) OR (nam thu)) va tinh va cua tre*.