@misc{Cayley_Arthur_(1821–1895)_On_1897,
 author={Cayley, Arthur (1821–1895)},
 volume={13},
 copyright={Public Domain},
 journal={Mathematical papers},
 address={Cambridge},
 howpublished={online},
 year={1897},
 publisher={Cambridge University Press},
 language={eng},
 type={Text},
 title={On the focals of a quadric surface},
 URL={http://rcin.org.pl/impan/Content/144984/PDF/WA35_176637_12807-13_Art902.pdf},
}