Perhaps you should try some spelling variations:
nam thuoc » nam thuc, cay thuoc, va thuoc
nha thuoc » nha nuoc, nhan thuc, nha hoc
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
va lanh » va lang, va danh, va hanh
dao cua » dai cua, day cua, dan cua
cua tre » cua te, cuu tre, cua triet
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 (nha thuoc))) OR (nam thu)) va lanh 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 (nha thuoc))) or (nam thu)) va lanh dao cua tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang o hai. hieu van ((((nam thuoc) OR (nha thuoc))) or (nam thu)) va lanh dao cua tre*.