Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nha thuoc, cay thuoc
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
va lanh » va danh, va hanh, va anh
dao cua » dai cua, day cua, dan cua
va lang » va nang, hoa lang
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
nang o » nang co, nang ho, nang ro
o hai » co hai, so hai, o lai

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang o hai. hieu van ((nam thuoc) OR (nam thu)) ((va lanh) OR (va lang)) dao cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang o hai. hieu van ((nam thuoc) or (nam thu)) ((va lanh) OR (va lang)) dao cua tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang o hai. hieu van ((nam thuoc) or (nam thu)) ((va lanh) OR (va lang)) dao cua tre*.