Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh dai » hanh tai, hanh dao, vanh dai
va triet » va thiet, va trien, ve triet
xay hoi » xa hoi, tay hoi, cay phoi
ky dang » ky nang, ky danh
truc va » thuc va, thuc vat, trung va
va hanh » van hanh, va thanh, va danh
ty dang » ty xang, ty hang, ty dong
va chim » va cham, va chi, ve chim
dai va » mai va

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ((ty dang) OR (ky dang)) xay hoi. hieu ((va chim) or (cao chat)) truc va hanh dai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ty dang) OR (ky dang)) xay hoi. hieu ((va chim) OR (cao chat)) truc va hanh dai va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((ty dang) OR (ky dang)) xay hoi. hieu ((va chim) or (cao chat)) truc va hanh dai va triet".
• Adding a wildcard symbol may retrieve word variants: toc sach ((ty dang) OR (ky dang)) xay hoi. hieu ((va chim) or (cao chat)) truc va hanh dai va triet*.