The resistors with question marks on them in series with the 0.1 ohms represent the lead and contact resistance through which the force current flows. Since the measurement circuit is directly across the 0.1 ohm resistor, and draws negligible current ( the two series resistors represent lead resistance to the meter, they are negligible compared to the meter resistance), it will measure the voltage only across the 0.1 ohms, and therefore the current may be calculated independently of the four resistors with question marks on them.
So although you obviously want to keep contact resistance low, you can't remove it, you just make the measurement in such a way that it's effect can be ignored.
If you look at the photo of a resistor used in a standards laboratory, the sense resistor terminals are large, with heavy leads and clamps for the force current. The sense wires are on the smaller inner terminals, closest to the sense resistor, and that is the key to making the system work, it's all in the position.
check out "photo of laboratory standard resistor" on the web,
cheers,
Richard
