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