5 Desargues, Bruillon-project d’une atteinte aux evenements des
      rencontres d’un cone avec un plan. 1639.  Edited and analyzed by
      Poudra, 1864.

    6 The term ‘pole’ was first introduced, in the sense in which we have
      used it, in 1810, by a French mathematician named Servois (Gergonne,
      Annales des Matheematiques, I, 337), and the corresponding term
      ‘polar’ by the editor, Gergonne, of this same journal three years
      later.

    7 Euler, Introductio in analysin infinitorum, Appendix, cap.  V. 1748.

    8 OEuvres de Desargues, t.  II, 132.

    9 OEuvres de Desargues, t.  II, 370.

   10 OEuvres de Descartes, t.  II, 499.

   11 OEuvres de Pascal, par Brunsehvig et Boutroux, t.  I, 252.

   12 Chasles, Histoire de la Geometrie, 70.

   13 OEuvres de Desargues, t.  I, 231.

   14 See Ball, History of Mathematics, French edition, t.  II, 233.

   15 Newton, Principia, lib. i, lemma XXI.

   16 Maclaurin, Philosophical Transactions of the Royal Society of
      London, 1735.

   17 Monge, Geometrie Descriptive. 1800.

   18 Poncelet, Traite des Proprietes Projectives des Figures. 1822. (See
      p. 357, Vol.  II, of the edition of 1866.)

   19 Gergonne, Annales de Mathematiques, XVI, 209. 1826.

   20 Steiner, Systematische Ehtwickelung der Abhaengigkeit geometrischer
      Gestalten von einander. 1832.

   21 Von Staudt, Geometrie der Lage. 1847.

   22 Reye, Geometrie der Lage.  Translated by Holgate, 1897.

   23 Ball, loc. cit. p. 261.