Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
va hanh » van hanh, va thanh, va danh
hieu va » lieu va, hieu qua
ty hang » ly hang, ty xang, thi hang
ly vang » ly hang, ly van, ly quang
cua tre » cua te, cuu tre, cua triet
va cam » va cham, va cac, va cao
xuc va » duc va, tuc va, luc va
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)) ((ly vang) or (ty hang)) xa hoi. hieu va cam xuc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ((ly vang) OR (ty hang)) xa hoi. hieu va cam xuc va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ((ly vang) or (ty hang)) xa hoi. hieu va cam xuc va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ((ly vang) or (ty hang)) xa hoi. hieu va cam xuc va hanh vi cua tre*.