Kemmer gives a development of a convenient formalism for the wave equation, different from the usual representation of Dirac's Hamiltonian.

Kemmer replies to a letter by Pauli. He writes on calculations on the regular representation of the Abel group and about irreducibility of this representation.

The letter contains some calculations on irreducible group representations.

Kemmer gives more calculations on the wave equation and makes a comparison with de Broglie's results.

Kemmer rejects an assumption made by Pauli.

Continuation of the letters of 8/9 May.

Critical remarks from Kemmer about Bhabha's calculations on the neutretto-meson theory and remarks on the Bremstrahlung of the meson.

Continuation of the letter of 8 May, Kemmer makes more remarks about the relation of his representation of the wave equation to de Boglie's.

This reply to Pauli's letter, concerns the representation of the wave equation with spin.

This reply to Pauli's letter is about the irreducibility of the n- group representation.