Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
cau thuc » cau truc, cuu thuc, can thuc
su triet » su viet, su tien, ve triet
lang xa » lang ha, dang xay, lang van
sach ky » sac ky, sach y, sach ty
va hanh » va thanh, va danh, ban hanh
nang ma » tang ma, sang ma, nang cao
van cau » van dau, van hau, van chat
hai su » hai vu, lai su, hai so

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky ((nang ma) or (lang xa)) hoi. hieu van cau thuc ((va hanh) or (van hanh)) hai su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky ((nang ma) OR (lang xa)) hoi. hieu van cau thuc ((va hanh) OR (van hanh)) hai su triet.
• Adding a wildcard symbol may retrieve word variants: thu sach ky ((nang ma) or (lang xa)) hoi. hieu van cau thuc ((va hanh) or (van hanh)) hai su triet*.