Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sang tao » hang tai
hieu va » lieu va, hieu qua
hoc can » hoc dan, hoc cao, hoc cac
tao hoi » tao khoi, tao boi, tay hoi
ky sang » ky nang, ky dang, ky tang
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: ((te sach) OR (toc sach)) ky sang tao hoi. hieu va cac ((duc tan) or (hoc can)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky sang tao hoi. hieu va cac ((duc tan) OR (hoc can)) hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ky sang tao hoi. hieu va cac ((duc tan) or (hoc can)) hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ky sang tao hoi. hieu va cac ((duc tan) or (hoc can)) hanh vi cua tre*.