I'm sorry to tell you I did not enjoy Sommerfeld. He was a bit on the high brow side and I can tell you one story about him that might explain my lack of enthusiasm. The story is about a very excellent American student who later got the Nobel Prize, van Vleck, who went as a young student to study in Munich. And there he was in the library, and in comes Sommerfeld. Excuse my German, I think you will understand it. Sommerfeld enters. van Vleck shows up and politely says- Guten Morgen, Herr Sommerfeld. He's rewarded with a none-too-pleasant grunt. Next time it happens Van Vleck says- Guten Morgen, Herr Professor. This time, Sommerfeld smiled a bit. On the following occasion, he said- Guten Morgen, Herr Doktor. Now, this time Sommerfeld said- Guten Morgen. But the last time Sommerfeld came in and van Vleck said- Guten Morgen, Herr Geheimrat. Well, Geheimrat means secret councilor. A very high title in Germany. And Sommerfeld looks at him- Aber Ihr Deutsch ist jeden Tag besser! But your German is improving every day! Well, that was not the kind of improvement that was my ambition. I studied, I sort of liked it, I was none too happy.