Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
hanh dai » hanh tai, hanh dao, vanh dai
su triet » su viet, su tien, ve triet
nang co » nang cao, nang doc, nang noi
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
nang o » nang ho, nang ro, nang x
van am » van nam, van lam, van dam
dai su » dai sua, dai so, dan su

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) or (toc sach)) ky ((nang o) OR (nang co)) hoc. hieu van am thuc va hanh dai su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky ((nang o) OR (nang co)) hoc. hieu van am thuc va hanh dai su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ky ((nang o) OR (nang co)) hoc. hieu van am thuc va hanh dai su triet".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky ((nang o) OR (nang co)) hoc. hieu van am thuc va hanh dai su triet*.