Readings on population and army size?

[Marja]

I think I need a bit more evidence before extrapolating from Greece in the 4th century B.C.E. to central Europe in the 4th century C.E. I wasn't relying on that alone, but much of the other data, was just too controversial [Italia, Aegyptus] and/or too incomplete [everywhere else] for comfort, and many of my other assumptions about the relationship between population densities in different areas were just too speculative.