Can you find the transfer function of two cascaded networks if you know their individual transfer functions?
In general you can't simply multiply the transfer functions together since the first section has a non-zero ouput impedance and the second section a finite input impedance. A transfer function of a network is only valid with it's output open-circuit.

Consider for example a section consisting of a single series resistor and a second section consisting of a single shunt resistor. Both have a transfer function of 1, but cascade them together and you have a potential divider. If you put a unity-gain buffer (with infinite input impedance and zero output impedance) between the sections then you could just multiply the transfer functions.

So knowing the individual sections' transfer functions is insufficient information to deduce the overall transfer function.