Richard Tolman, "On the Problem of the Entropy of the Universe as a Whole", in the Physical Review, June 15, 1931, volume 37, number 12, pp 1639-1660, in the original printed wrappers. Very good copy. $195
See The Penetration of Charged Particles Through Matter (1912 - 1954). edited by J. Thorsen, pp. 254ff
See: About Time: Cosmology and Culture at the Twilight of the Big Bang, by Adam Frank
Also in this issue: R.M. Langer and N. Rosen, "The Neutron", pp 1579-1583.