To cite package ‘cycle’ in publications use:

  Futschik M, Herzel H (2008). “Are we overestimating the number of
  cell-cycling genes? The impact of background models on time series
  analysis.” _Bioinformatics_, 1063-1069. <http://cycle.sysbiolab.eu>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Are we overestimating the number of cell-cycling genes? The impact of background models on time series analysis},
    author = {Matthias Futschik and Hanspeter Herzel},
    journal = {Bioinformatics},
    number = {24(8)},
    pages = {1063-1069},
    year = {2008},
    url = {http://cycle.sysbiolab.eu},
  }