@misc{Ball_Walter_William_Rouse_(1850–1925)_An_1893,
 author={Ball, Walter William Rouse (1850–1925)},
 copyright={Public Domain},
 address={London},
 address={New York},
 howpublished={online},
 year={1893},
 publisher={Macmillan and Co.},
 language={eng},
 title={An essay on Newton's "Principia"},
 type={Text},
 URL={http://www.rcin.org.pl/Content/235304/6087.pdf},
}