1. Abdi, A. 2007. The eigen-decomposition: Eigenvalues and eigenvectors. In Encyclopedia of measurement and statistics, ed. N. Salkind, 305–9. Thousand Oaks, CA: Sage.
2. Alexandroff P. and H. Hopf. 1935. Topologie I [Topology I]. Berlin: Springer.
3. The law of excluded middle: To be or not to be;Arlinghaus S.;Solstice: An Electronic Journal of Geography and Mathematics,2022
4. QR-graphs: Codes and nodes, places and spaces;Arlinghaus S.;Solstice: An Electronic Journal of Geography and Mathematics,2022
5. Arlinghaus S. L. W. C. Arlinghaus and F. Harary. 2002. Graph theory and geography: An interactive view. Hoboken NJ: Wiley-Interscience.