1. See Werner Heisenberg, "Zur Quantentheorie der Multiplettstruktur und der anomalen Zeemaneffekte," Zeitschrift far Physik 32 (1925), pp. 841-860 [reprinted in Werner Heisenberg, Gesammelte Werke: Collected Works,edited by W. Blum, H.P. Dürr, and H. Rechenberg, vol. A I, pp. 306-328]. The paper was received on April 10, 1925 and published in issue no. 10/11 of June 30, 1925. Cf., e.g., Friedrich Hund's introduction to Heisenberg's papers on atomic and molecular structure (1922-1925) in Heisenberg, Collected Works,vol. A I, pp. 127-133, and Jagdish Mehra and Helmut Rechenberg's The Discovery of Quantum Mechanics 1925,volume 2 of their Historical Development of Quantum Theory (Berlin: Springer, 1982), section 1I.5
2. cf. also chapter V, pp. 261ff., for an account of Heisenberg's discovery of quantum mechanics in the second half of June and early July, 1925.
3. See, e.g., Armin Hermann, Werner Heisenberg in Selbstzeugnissen und Bilddokumenten (Reinbek: Rowohlt, 1976); David Cassidy, Uncertainty: The Science and Life of Werner Heisenberg (New York: Freeman, 1992), pp. 46–48, chapters 6 to 8; M. Stöckler, C. Liesenfeld, and H. Seidel, in Bodo Geyer et al. (eds.), Werner Heisenberg: Physiker und Philosoph,pp. 335–355; for the physics context, see in particular Paul Forman, “Alfred Landé and the Anomalous Zeeman Effect, 1919–1921,” Historical Studies in the Physical Sciences 2 (1970), pp. 153–261; Edward MacKinnon, “Heisenberg, Models, and the Rise of Matrix Mechanics,” Historical Studies in the Physical Sciences 8 (1977), pp. 137–188; Daniel Serwer, “Unmechanischer Zwang: Pauli, Heisenberg, and the Rejection of the Mechanical Atom, 1923–1925,” Historical Studies in the Physical Sciences 8 (1977), pp. 189–256; and the secondary texts mentioned in notes 1 and 3. See also T.S. Kuhn’s interview with Heisenberg, November 30, 1962 in Sources for History of Quantum Physics.
4. Apart from the more specific studies mentioned in the previous note, I have also checked broader overviews on the development of quantum theory and quantum mechanics, such as Max Jammer, The Conceptual Development of Quantum Mechanics (New York: McGraw Hill, 1966), chapter 3; Friedrich Hund, Geschichte der Quantentheorie,third edition (Mannheim: Bibliographisches Institut, 1984), chapters 9 to 12; Mehra and Rechenberg, op.cit. (note 1); Olivier Darrigol, From c-numbers to q-numbers: The Classical Analogy in the History of Quantum Mechanics (Berkeley: University of California Press, 1992), chapters 7 to 10.
5. The German terms used by Heisenberg are “modellmäßige Bilder” and “Schema,” later he also introduces “quasimechanical models of schemes” with “Bild” and “Schema” used interchangeably, while Hertz only uses the word “Bild”: I will consistently leave the term “Bild” untranslated, and translate “Schema” as “scheme,” and “Modell” as “model.”