 Over Pythagorese en bijna-Pythagorese driehoeken en een generatieproces met behulp van unimodulaire matrices by F. J. M. Barning

Mathematisch Centrum report ZW 1963-011, August 1963. Original institutional scan: ir.cwi.nl/pub/7151/7151D.pdf

Section 1, printed pages 3–5, displays the three unimodular generating matrices and the unique-generation theorem; the proof continues on page 7 after the inserted diagram/table. Barning puts the even leg first, with root (4,3,5).