2nd Army or 4th Army? 

So I've been slowly eating through Barbarossa Derailed: Battle of Smolensk, Volume 2 (by D. Glantz) and it consistently states that Army Group Centre (specifically as of August and September 1941) was made up of 9th Army, 2nd Army, 2nd Panzer Group (or Army Group Guderian or Panzer Group Guderian), 3rd Panzer Group, and some other secondary Armies. It never mentions of 4th Army, as far as I have read or glanced through. Several Wikipedia articles all agree 4th Army was there. I'm baffled. Not sure, which it is anymore. Glantz or the many Wikipedia articles? Can some other editor dig into this and make any needed changes.