Perhaps you should try some spelling variations:
nam thuoc » nam thu, nha thuoc, cay thuoc
sach thu » sach thue, sach thieu, sach tham
nam thuc » am thuc, nam thu, nam tu
hieu van » hieu va, thien van, lieu va
tinh va » tich va, trinh van, trinh vat
va tinh » may tinh
tu sach » thu sach, su sach, te sach
nang ma » tang ma, sang ma, nang cao
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 thu ((nang ma) or (nang x)) hoi. hieu van ((nam thuoc) OR (nam thuc)) va tinh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thu ((nang ma) OR (nang x)) hoi. hieu van ((nam thuoc) OR (nam thuc)) va tinh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach thu ((nang ma) or (nang x)) hoi. hieu van ((nam thuoc) OR (nam thuc)) va tinh va cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach thu ((nang ma) or (nang x)) hoi. hieu van ((nam thuoc) OR (nam thuc)) va tinh va cua tre*.