Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
hanh hai » thanh hai, nhanh hai, hang hai
va triet » va thiet, va trien, ve triet
lang xa » lang ha, dang xay, lang van
van cau » van dau, van hau, van chat
cau duc » cao duc, cau luc, chu duc
va hanh » van hanh, va thanh, va danh
hai va » hai van, thai va, hoi va

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 x) or (lang xa)) hoi. hieu van cau duc va hanh hai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky ((nang x) OR (lang xa)) hoi. hieu van cau duc va hanh hai va triet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ky ((nang x) or (lang xa)) hoi. hieu van cau duc va hanh hai va triet*".