How to use SC circuit to implement the following expression?

[princerock]

Y=(X1+X2-X3)*(1/(z-1))

X1,X2,X3 are inputs. z means in z domain. Use no more than 2 sampling capacitors and 1 op amp.

I think this problem is the sc implementation of adder and scaler circuit. Where can I find materails about this?

Thank you for your help!