1. Clebsch 1871, p. 3.
2. See Wußing 1984, p. 25.
3. First steps towards an analytical geometry can be traced via E. Torricelli, G. Galilei, J. Kepler, N. Oresme to Appolonius of Perga. — See Böhm et. al. 1975, p. 16sqq.
4. See Struik 1987, 96sqq.
5. See Clebsch 1871, p. 10.