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

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 hoc. ((hieu van) OR (hieu va)) dau 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 hoc. ((hieu van) OR (hieu va)) dau 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 hoc. ((hieu van) OR (hieu va)) dau thuc va hanh dai su triet".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky nang o hoc. ((hieu van) OR (hieu va)) dau thuc va hanh dai su triet*.