One dealing with the previously mentioned French campaign, another looking at the Balkans, North Africa and continuing the Barbarossa, another with pre-war and Poland.
The "Lang" volume will be focused on how the production was different in each of the three factories that were involved during this period. In Vol 3 & 4 the tables illustrate generic production and overall orders, helpful for identifying vehicles up to a point. However vehicles with chassis numbers visible have revealed anomalies to these tables.
I have been making new table showing monthly chassis numbers for each factory, which may help show how changes were implemented at different rates at each factory.