Perhaps you should try some spelling variations:
cam truc » cau truc, nam truc, lam truoc
hieu van » hieu va, thien van, lieu va
su sach » vu sach
va hanh » van hanh, va thanh, va danh
truc va » thuc va, thuc vat, trung va
van cam » van nam, van lam, van cau
cua tre » cua te, cuu tre, cua triet
so sach » so sanh, bo sach, co sach
nang ma » tang ma, sang ma, nang cao
vi cua » vai cua, di cua

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

• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) v ((nang x) OR (nang ma)) hoi. hieu van cam truc va hanh vi cua tre~.
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (so sach)) v ((nang x) or (nang ma)) hoi. hieu van cam truc va hanh vi cua tre*.