Perhaps you should try some spelling variations:
bao thuc » cao thuoc, am thuc, va thuc
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
va hanh » van hanh, va thanh, va danh
yu hang » yu zhang, yu pang, yu wang
cua tre » cua te, cuu tre, cua triet
co hoi » co hoc, co loi
y hang » ly hang, ty hang, _ hang
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: su sach ((y hang) OR (yu hang)) co hoi. hieu van ((bao luc) or (bao thuc)) va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((y hang) OR (yu hang)) co hoi. hieu van ((bao luc) OR (bao thuc)) va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((y hang) OR (yu hang)) co hoi. hieu van ((bao luc) or (bao thuc)) va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((y hang) OR (yu hang)) co hoi. hieu van ((bao luc) or (bao thuc)) va hanh vi cua tre*.