1. Andrew, J. (1881). The pendulograph: A series of bi-pendulum writings of the twenty ratios of the musical system; or, sound see in the silence. George Bell and Sons.
2. Freeman, W. J. (1991). The Physiology of Perception. Le Scienze, apr. 1991, n. 272, a. XXIV, v. XLVI.
3. Gay, F. (2000). Intorno agli omolografi, strumenti e modelli per la geometria descrittiva. Quaderni IUAV, 13, 2000.
4. Goold, J., Benham, C. E., Kerr, R., & Wilberforce, L. R. (1909). Harmonic vibrations and vibration figures. Herbert C. Newton - Newton & Co.
5. https://michitres.com/2-3-pendulum-designs/—May 2022a/