Layer-wise differences in Mouse Reference Atlas Entorhinal Area vs Isocortex

I was trying to understand the reasoning behind layer annotations in lateral and medial Entorhinal Area compared to isocortex. I have read that initial differentiation between these regions were based on the calbindin expression from the TECHNICAL WHITE PAPER:
ALLEN MOUSE COMMON COORDINATE FRAMEWORK. But later on, how does layer annotations made within entorhinal regions? Is there a specific marker that guides it ?