I am reading a research note"quantum hall effect" from arxiv website. I'm told that the resistance of a 2D conductor depends in general on the so-called aspect ratio L/W via some factor f(L/W) . However, in the case of the transverse Hall resistance it is the length of the conductor itself that plays the role of the cross section, such that the Hall resistivity and the Hall resistance truely coincide, i.e. f = 1. I don't really understand about the transverse hall resistance "the lenth of the condutor itself plays the role of cross section ".