1. G. Di Battista, P. Eades, R. Tamassia, I. G. Tollis. Graph Drawing: algorithms for the visualization of graphs. Prentice Hall, 1999.
2. Lect Notes Comput Sci;F. Bertault,1984
3. N. Biggs, E. K. Lloyd, R. J. Wilson. Graph Theory 1736-1936 OUP, 1976.
4. L. Euler. Lettres a Une Princesse d’Allemagne, vol 2. 1761. Letters No. 102-108.
5. J. Gil, J. Howse, S. Kent. Formalising Spider Diagrams. Proc. IEEE Symposium on Visual Languages (VL99), Tokyo, Sept 1999. IEEE Comp Soc Press, 130–137.