Steps intermediate between Gamma-4 (20) and (21):

(20) with substitutions; "replica" in red (20.1)
     
Deiterate the "replica" (20.2)
     
(20.2). Rngm, Rnbc (20.3)

Graph (20.3) is the same as graph (21) in the main sequence. Note that the original of (21) in the typed version of this paper contains an error: there is an extraneous alpha cut around the left member of that version of the graph.