Perhaps you should try some spelling variations:
cua triet » cua viet, su triet, va triet
hieu van » hieu va, thien van, lieu va
can thuc » dan thuc, cay thuc, san thuc
van thuc » va thuc, dan thuc, van thu
dan hanh » dang hanh, dan khanh, dan thanh
so sach » so sanh, bo sach, co sach
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach y ((nang xa) or (nang ma)) hoi. hieu van ((can thuc) OR (van thuc)) dan hanh vi cua triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y ((nang xa) OR (nang ma)) hoi. hieu van ((can thuc) OR (van thuc)) dan hanh vi cua triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach y ((nang xa) or (nang ma)) hoi. hieu van ((can thuc) OR (van thuc)) dan hanh vi cua triet".
• Adding a wildcard symbol may retrieve word variants: so sach y ((nang xa) or (nang ma)) hoi. hieu van ((can thuc) OR (van thuc)) dan hanh vi cua triet*.