@misc{Cayley_Arthur_(1821–1895)_On_1895,
 author={Cayley, Arthur (1821–1895)},
 copyright={Public Domain},
 journal={Mathematical papers},
 address={Cambridge},
 howpublished={online},
 year={1895},
 publisher={Cambridge University Press},
 language={eng},
 type={Text},
 title={On a differential formula connected with the theory of confocal conics},
 URL={http://www.rcin.org.pl/Content/135408/PDF/WA35_168133_12807-8_Art67.pdf},
}