Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dam thuc » am thuc, dan thuc, nam thuc
thi van » thi lan, thi hanh, thi nang
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
van dam » van nam, van dao, van dau
nang o » nang co, nang ho, nang ro
dao su » dao suu, dan su, da 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. thi van dam thuc va hanh ((dao su) OR (cao su)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky nang o hoc. thi van dam thuc va hanh ((dao su) OR (cao su)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ky nang o hoc. thi van dam thuc va hanh ((dao su) OR (cao su)) triet".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky nang o hoc. thi van dam thuc va hanh ((dao su) OR (cao su)) triet*.