I am indebted to Professor Joseph Zund for introducing me to Greek ladders several years ago, and I thank Professors David Pengelley and Fred Richman for their very useful comments. The material in this article was presented at the MAA Southwestern Annual Conference, Western New Mexico University, Silver City, NM, April 3-4, 2009.
Robert J. Wisner is Professor Emeritus in the Department of Mathematical Sciences at New Mexico State University. He was founding editor of SIAM Review, the only one of the 14 journals of the Society for Industrial and Applied Mathematics (SIAM) designed to appeal to all of its members. Wisner also has authored or co-authored numerous K-12 textbooks for Scott Foresman and Company; was Consulting Editor for Mathematics for Brooks/Cole for over 25 years; and recently co-authored a series of interactive pre-calculus textbooks, available on CD from Hardy Calculus.
 Leonard Eugene Dickson, History of the Theory of Numbers, vol. II, Chelsea Publishing Company, New York, 1919, p. 341.
 David Fowler, The Mathematics of Plato's Academy, A New Reconstruction (2nd ed.), Oxford University Press, 2003, pp. 57-58.
 Shaun Gilberson and Thomas J. Osler, "Extending Theon's Ladder to Any Square Root," College Math. J. 35 (2004) pp. 222-226.
 Russell Jay Hendel, "Approaches to the Formula for the \(n\)-th Fibonacci Number," College Math. J. 25 (1994) pp. 139-142.
 H. W. Turnbull, The Great Mathematicians, Simon and Shuster, New York, 1962, pp. 28-30.
 G. C. Vedova, "Notes on Theon of Smyrna," Amer. Math. Monthly 58 (1951) pp. 675-683.
 Robert J. Wisner, "Square Roots: Greek Ladders, Farey Fractions, and Pascal's Triangle," The AMATYC Rev. 23 (2002) no. 2, pp. 53-60.
 John J. O'Connor and Edmund F. Robertson, “Roger Cotes,” MacTutor History of Mathematics Archive, http://www-history.mcs.st-andrews.ac.uk/Biographies/Cotes.html