Chudnovsky, David V. và Chudnovsky, Gregory V., "Approximations and Complex Multiplication According to Ramanujan", trong Ramanujan Revisited (G.E. Andrews et al. Eds), Academic Press, 1988, 375–396, 468–472
Cox, David A., "The Arithmetic-Geometric Mean of Gauss", L' Ensignement Mathematique, 30(1984) 275–330
Engels, Hermann, "Quadrature of the Circle in Ancient Egypt", Historia Mathematica 4(1977) 137–140
Euler, Leonhard, "On the Use of the Discovered Fractions to Sum Infinite Series", trong Introduction to Analysis of the Infinite. Book I, dịch từ tiếng Latin bởi J. D. Blanton, Springer-Verlag, 1964, pp 137–153
Heath, T. L., The Works of Archimedes, Cambridge, 1897; in lại trong The Works of Archimedes with The Method of Archimedes, Dover, 1953, pp 91–98
Huygens, Christiaan, "De Circuli Magnitudine Inventa", Christiani Hugenii Opera Varia I, Leiden 1724, pp 384–388
Lay-Yong, Lam và Tian-Se, Ang, "Circle Measurements in Ancient China", Historia Mathematica 13(1986) 325–340
Lindemann, Ferdinand, "Ueber die Zahl pi", Mathematische Annalen 20(1882) 213–225
Matar, K. Mukunda, and Rajagonal, C., "On the Hindu Quadrature of the Circle" (Appendix by K. Balagangadharan). Journal of the Bombay Branch of the Royal Asiatic Society 20(1944) 77–82
Niven, Ivan, "A Simple Proof that pi Is Irrational", Bulletin of the American Mathematical Society, 53:7 (July 1947), 507
Ramanujan, Srinivasa, "Modular Equations and Approximations to pi", Journal of the Indian Mathematical Society, XLV, 1914, 350–372. In lại trong G.H. Hardy, P.V. Sehuigar, và B. M. Wilson (eds), Srinivasa Ramanujan: Collected Papers, 1962, 23–29
Shanks, William, Contributions to Mathematics Comprising Chiefly of the Rectification of the Circle to 607 Places of Decimals, 1853, pp. i–xvi, 10
Tropfke, Johannes, Geschichte Der Elementar-Mathematik in Systematischer Darstellung (The history of elementary mathematics), BiblioBazaar, 2009 (in lại), ISBN 978-1-113-08573-3
Viete, Francois, Variorum de Rebus Mathematicis Reponsorum Liber VII. F. Viete, Opera Mathematica (in lại), Georg Olms Verlag, 1970, 398–401, 436–446
Wagon, Stan, "Is Pi Normal?", The Mathematical Intelligencer, 7:3(1985) 65–67
Wallis, John, Arithmetica Infinitorum, sive Nova Methodus Inquirendi in Curvilineorum Quadratum, aliaque difficiliora Matheseos Problemata, Oxford 1655–6. In lại trong tập 1 (tr. 357–478) của Opera Mathematica, Oxford, 1693
Zebrowski, Ernest, A History of the Circle: Mathematical Reasoning and the Physical Universe, Rutgers Univ Press, 1999, ISBN 978-0-8135-2898-4
