Petermann, A. (August), 1822-1878. Weltkarte in Nordpolar-Sternprojektion nach einer Idee von Dr. G. Jäger, in Wien., map, 1865; (https://texashistory.unt.edu/ark:/67531/metapth190399/m1/1/: accessed June 11, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .