Perhaps you should try some spelling variations:
hang tai » hang va, dung tai
tai khoa » da khoa, noi khoa
hieu van » thien van, lieu va, hieu ve
van hanh » van thanh, ban hanh, van anh
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
ky hang » ky nang, ly hang, ky dang
hieu va » lieu va, hieu qua
cam duc » cam xuc, cao duc, pham duc
va hanh » va thanh, va danh, ban hanh
cua tre » cua te, cuu tre, cua triet
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 hang tai khoa. ((hieu van) or (hieu va)) cam duc ((va hanh) OR (van hanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky hang tai khoa. ((hieu van) OR (hieu va)) cam duc ((va hanh) OR (van hanh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky hang tai khoa. ((hieu van) or (hieu va)) cam duc ((va hanh) OR (van hanh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ky hang tai khoa. ((hieu van) or (hieu va)) cam duc ((va hanh) OR (van hanh)) vi cua tre*.