Nilsson reinterprets Rydberg's "triplets". He gives a modern level scheme.

Nilsson reports on Siegbahn's response to Pauli's inquiries about Rydberg's new elements of 1913.

Nilsson encloses a photo of J R Rydberg.

Nilsson makes remarks on Rydberg's 1913 postulate of two new elements. He talks about the "wechselsatz' multiplet.

Källén writes on his recent attempts to simplify the calculations on quantum electrodynamics.

Källén talks about calculation on an integral-representation of the S$_{c}$-function, avoiding the complex method of integration.

Källén encloses a manuscript dealing with the contents of his last letter of the 12 December 1949, in addition to a calculation on bosons in an external field.

Källén talks about some general observations on the mathematical formalism of the Lee model.