Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
ky hang » ly hang, ky dang, ty hang
van cam » van nam, van lam, van cau
va hanh » va thanh, va danh, ban hanh
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet

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

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