CZ:Ref:DOI:10.1093/brain/103.2.221

Rockel, A. J.; R. W. Hiorns & T. P. S. Powell (1980), "The Basic Uniformity in Structure of the Neocortex", Brain 103 (2): 221–244, DOI:10.1093/brain/103.2.221 ^[e]

A well-cited paper concluding that

1. "The intrinsic structure of the neocortex is basically more uniform than has been thought and that differences in cytoarchitecture and function reflect differences in connections."
2. The cerebral cortex is organized in columns
3. The number of neurons underneath equally sized patches of cortical surface area is approximately identical (around 147,000 per $mm^{2}$) across mammalian species, with the exception of the primary visual cortex in primates.

Point number 3 has been refuted by a number of studies (e.g. Herculano-Houzel et al., 2008; see also references therein), as summarized by Rakic 2008.