As part of my first article in the Reviews of Modern Physics I tried to figure that and found that the number of resonance's would increase exponentially with the energy of the neutron and the energy of the neutron when... of a slow neutron when entering the nucleus is some 7 or 8 million electron volts, because that's what it would be bound by when it finally is captured. And at such an excitation energy you get a very high density of levels. Then very soon, Weisskopf introduced the concept of entropy, and said 'Well, the number of levels is e^s where s is the entropy', and in my first article I calculate the entropy as a function of excitation energy and atomic number. I also made a mistake in that but I think it's not important to dwell on that. In fact, one thing I should mention, I sent that paper to Peierls to look at, and Peierls was horrified by the sloppiness I had... I had used, and wrote me back a letter which went, taking off from the Dreigroschenoper in Germany; 'Erst komt das denken, dann das Integral.' First think and then carry out an integral.