Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
cua viet » ca viet, cua vat, cua dieu
hieu van » hieu va, thien van, lieu va
va dinh » van dinh, va kinh, va tinh
va danh » va dan, va hanh, dia danh
sach ky » sac ky, sach y, sach ty
van am » van nam, van lam, van dam
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky nang o hoi. hieu van am thuc ((va danh) or (va dinh)) hai ((cua viet) OR (hoa viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang o hoi. hieu van am thuc ((va danh) OR (va dinh)) hai ((cua viet) OR (hoa viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky nang o hoi. hieu van am thuc ((va danh) or (va dinh)) hai ((cua viet) OR (hoa viet))".
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang o hoi. hieu van am thuc ((va danh) or (va dinh)) hai ((cua viet) OR (hoa viet))*.