Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
sach ky » sach y, sach ty, sach kem
cao hoi » cau hoi, co hoi, cao hoc
van cam » van nam, van lam, van cau
cam tuc » cam xuc, cam tu, nam thuc
va hanh » va thanh, va danh, ban hanh
sac ky » cac ky, sai ky
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 ky) or (sac ky)) nang cao hoi. hieu van cam tuc ((va hanh) OR (van hanh)) vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ky) OR (sac ky)) nang cao hoi. hieu van cam tuc ((va hanh) OR (van hanh)) vi cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach ky) or (sac ky)) nang cao hoi. hieu van cam tuc ((va hanh) OR (van hanh)) vi cua vat".
• Adding a wildcard symbol may retrieve word variants: so ((sach ky) or (sac ky)) nang cao hoi. hieu van cam tuc ((va hanh) OR (van hanh)) vi cua vat*.