W(alter) Gordon, Der Comptoneffekt nach der Schrödingerschen Theorie”, offprint from Zeitschrift fur Physik, 40, 1-2, Berlin, Julius Springer, 1926, pp 117-133. Original wrappers. Very Good.  SOLD

“…the Klein–Gordon equation correctly describes the spinless relativisitic composite particles, like the pion. On July 4, 2012 CERN announced the discovery of the Higgs boson. Since the Higgs boson is a spin-zero particle, it is the first observed ostensibly elementary particle to be described by the Klein–Gordon equation.”–Wiki

See also:

• H. Kragh: “Equation with Many Fathers, the Klein-Gordon Equation in 1926”, AmJ Phys 52(100), pp 1024, 1984.  (Also citing Vladimir Fock, Johann Kudar, Théophile de Donder and Frans-H. van den Dungen, and Louis de Broglie. )
• Weisstein, Eric W. “Klein-Gordon Equation.” From MathWorld–A Wolfram Web Resource.
• Jiří Bičák, Tomáš Ledvinka, eds: Relativity and Gravitation: 100 Years after Einstein in Prague, p. 268.
• Victor E. Borisenko, Stefano Ossicini, What is What in the Nanoworld: A Handbook on Nanoscience and Nanotechnology

ALSO:

W(alter) Gordon, “Zur Lichtfortpflanzung nach der Relativitätstheorie”, offprint from Annalen der Physik, IV/72, 1923, published by Barth in Leipzig., p (421)-456. Original wrappers. Very Good.  SOLD

“…the main reason why Gordon’s paper should have been considered at the time of its appearance and remembered thereafter is, in our opinion, another one and, to our knowledge, it has remained completely unnoticed by everybody [in spite of 250+ citations?], if one excludes the attentive reviewer of Gordon’s article for “Physikalische Berichte”: that paper contains a clear-cut argument for selecting, through a clever reductio ad vacuum, the stress-energy-momentum tensor of the electromagnetic field in non-dispersive matter, provided that the latter be homogeneous and isotropic when considered in its rest frame “–A forgotten argument by Gordon uniquely selects Abraham’s tensor as the energy-momentum tensor for the electromagnetic field in homogeneous, isotropic matter. S. Antoci and L. Mihich Dipartimento di Fisica “A. Volta” – Pavia, Italy