@misc{Cayley_Arthur_(1821–1895)_On_1891,
 author={Cayley, Arthur (1821–1895)},
 volume={4},
 copyright={Public Domain},
 address={Cambridge},
 journal={Mathematical papers},
 howpublished={online},
 year={1891},
 publisher={University Press},
 language={eng},
 title={On contour and slope lines},
 title={The collected mathematical papers of Arthur Cayley. Vol. 4},
 type={Text},
 URL={http://rcin.org.pl/Content/125138/PDF/WA35_152783_12807-4_On-contour-and.pdf},
}