# Impervious nature of solid matter due to quantum degeneracy pressure

On Wikipedia the following statement is made without reference:

Freeman Dyson showed that the imperviousness of solid matter is due to quantum degeneracy pressure rather than electrostatic repulsion as had been previously assumed.

Can anyone find the appropriate reference(s)?

-
Terry took a pop-sci crack at the issue on a earlier question. Also related: physics.stackexchange.com/q/1077/520 . –  dmckee May 17 '12 at 17:24