“…5.1 Gauss' letter to Schumacher [1836] The extensive epistolary correspondence between the great mathematician and scientist, Carl Friedrich Gauss (1777-1855), and the Danish-German astronomer, Heinrich Christian Schumacher (1780-1850), published in a series of volumes in the 1860s, has been a valuable source for historians and mathematicians. Gauss' connection to the Steiner tree problem was discussed by Schreiber (1986), and the story has been told in a number of other papers and books (Cheng et al (2004), Cieslik (2004a), Cieslik (2004b), Du and Wu (2007), Gander et al (2008) and Scriba and Schreiber (2010)).…”