| Apatow, R. | The Tetraktys, The Cosmic Paradigm Af the ancient Pythagoreans | 1999 |
| Arcellaschi, A. | Maitres et exclaves dans les Bacchides | 1981 |
| Barocelli, F. | Raffaelo e la Tetractys di Pitagora'in | 2003 |
| Bertolini, M. | LA RUOTA ARMONICA. PITAGORISMO E SCIENZA MODERNA IN FEDERICO BORROMEO | 2016 |
| Beydts, A. | De l'importance de la Tetractys sur les artefacts romains | 2015 |
| Blackstone, B. | Keats and the Tetraktys | 1953 |
| Boehm, F. | Die Schrift des Giglio Gregorio Giraldi uber die Symbole des Pythagoras | 1913 |
| Boreas, T. | Pythagoreia symbola | 1927 |
| Bostock, G. | The sacred tetractys | |
| Boyance, P. | Note sur la tetractys | 1951 |
| Caramella, S. | Simbolismo pitagorico | 1940 |
| Comia, G. | Rediscovering the Mystical Significance of Pythagorean Tetractys | 2024 |
| Cumont, F. | Lucrece et le symbolisme pythagoricien des enfers | 1920 |
| Davie, J.R. | Pythagoras in perspective | 1959 |
| Denom, G. | LES QUATRE ARTS D'APOLLON Introduction à l’ésotérisme de la tétractys | 2021 |
| Deretić, I. | The Number Ten Reconsidered: Did the Pythagoreans Have an Account of the Dekad? | 2020 |
| Domaradzki, M. | Sull'allegoresi simbolica del primo pitagorismo | 2013 |
| Drysdall, D. | On pythagorean symbols | 1577 |
| Dupuis, J. | Note sur le serment des pythagoriciens | 1894 |
| Fitger, M. | The Tetractys and the Hebdomad: Blavatsky’s Sacred Geometry | 2020 |
| Gansinger, M.A.M. | Supreme Mathematics The Five Percenter Model of Divine Self-Realization and Its Commonalities to Interpretations of the Pythagorean Tetractys in Western Esotericism | 2023 |
| Goettling, C.W. | Die Symbole des Pythagoras | 1851 |
| Gyraldi, L.G. | Philosophi Pythagorae symbolorum interpretatio | 1696 |
| Haase, R. | Das pythagoreische Lambdoma | 1974 |
| Heninger, S.K. | Some Renaissance Versions of the Pythagorean Tetrad | 1961 |
| Heninger, S.K. | Pythagorean Symbola in Erasmus"Adagia | 1968 |
| Jahoda, G. | Die Doppelgestalt der pythagoreischen Tetraktys | 1971 |
| Josserand, C. | Les Symboles pythagoriciens de collenuccio | 1932 |
| Kalvesmaki, J. | Excursus B. The Pythagorean Symbol of the Τετρακτύς | |
| Kirschner, E. | Doppelsieg des Pythagoras | |
| Koller, H. | Harmonie und Tetraktys | 1959 |
| Latendorf, F. | Ein Symbolum des Pythagoras | 1855 |
| Latura, G.B. | Kepler's Sesquialter and the Tetraktys of Pythagoras | |
| Lauenstein, H. | Ursprunge des architektonischen Proportionenkanons | |
| Levin, F.R. | Unity in Euclid's Sectio Canonis | 1990 |
| Limburg-B P. van | Les symbols de Pythagore | 1839 |
| Losev, A. | The Tetractys or This_Square is a Triangle | |
| Lyng, G.W. | Om Pythagoreismen | 1867 |
| Major, E. | Das "Symbolum Pythagoricum" des Conrad Lycosthenes | 1943 |
| Marcovich, M. | Sobre algunos obsuros symbola de los Pitagoricos | 1865 |
| Matieu, M. | CONJUGAISON HARMONIQUE, TÉTRAKTYS ET MÉDIÉTÉS PYTHAGORICIENNES | 2021 |
| Miller, G.A. | A wide-spread error relating to the pythagoreans | 1935 |
| Plebe,A. | Il simbolismo nei pitagorici | 1956 |
| Purucker, G. de | Hierarchieeen: een van de verloren sleutels van de esoterische filosofie. De heilige tetraktys van Pythagoras | |
| Saffrey, H.D. | Une collection meconnue de symboles pythagoriciens | 1967 |
| Schulze, W. | Tetraktys ein vergessenes Wort der Philosophie | 1983 |
| Schulze, W. | Ein harmonikales Analogon: Leibnitz' Stammbaummodell in der Dissertatio de Arte Combinatoria | 1987 |
| Schwabe, J. | Hans Kayers letzte Entdeckung: die pythagorische Tetraktys auf Raffaels "Schule von Athen" | 1966 |
| Schwabe, J. | Arithmetische tetraktys, lambdoma und Pythagoras | 1967 |
| Thom, J.C. | Don't walk on the highways": the pythagorean Akousmata and early Christian literature | 1994 |
| Vida, G.L. della | Sentenze Pitagoriche in versione Siriaca | 1910 |
| Vitek, T. | The origins of the pythagorean symbola | 2009 |
| Vonessen, F. | Die pythagoreischen Symbole | 1968 |
| Vuilleumiers Laurens, F. | Filippo Beroaldo. Symbola pythagorae moraliter explicata | 2000 |
| Weinreich, O. | Zur Wiener Kybele statuette Reliositat | 1921 |
