@Book{Perron54a,
  author = 	 {Oskar Perron},
  title = 	 {Die {L}ehre von den {K}ettenbr{\"u}chen - vol. 1 : 
                  element{\"a}re {K}ettenbruche},
  publisher = 	 {B.G. Teubner},
  year = 	 1954
}