Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nam thu, cay thuoc
nha thuoc » nha nuoc, nhan thuc, nha hoc
van hanh » van thanh, ban hanh, van anh
dang xay » dang van, van xay
tu sach » thu sach, su sach, te sach
hanh va » hang va, hanh vi
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
hieu le » hieu ve, hieu he, hieu ly
nang xa » nang x, lang xa, nang ma
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 (dang xay)) hoi. hieu le ((nam thuoc) OR (nha thuoc)) van hanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (dang xay)) hoi. hieu le ((nam thuoc) OR (nha thuoc)) van hanh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang xa) or (dang xay)) hoi. hieu le ((nam thuoc) OR (nha thuoc)) van hanh va cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang xa) or (dang xay)) hoi. hieu le ((nam thuoc) OR (nha thuoc)) van hanh va cua tre*.