Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
thanh va » thanh van, hanh va, thanh ha
su triet » su viet, su tien, ve triet
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
cam tuc » cam tu, nam thuc, dam thuc

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky ((nang x) or (nang ma)) hoi. hieu van ((cam tuc) OR (cam xuc)) ban thanh va su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang x) OR (nang ma)) hoi. hieu van ((cam tuc) OR (cam xuc)) ban thanh va su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang x) or (nang ma)) hoi. hieu van ((cam tuc) OR (cam xuc)) ban thanh va su triet".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang x) or (nang ma)) hoi. hieu van ((cam tuc) OR (cam xuc)) ban thanh va su triet*.