Information Concerning Crystal Structure from Data on Magnetic Susceptibilities

Reminiscences of the first decade of quantum mechanics

“…Obviously fitting such a situation required a rather involved theory. There were, however certain qualitative features of Jordahl's thesis [44] that were correct and interesting. He developed what is sometimes called Van Vleck degenerate perturbation theory in greater detail than I did when I first presented it in an earlier paper on I-type doubling [33].…”