To cite package 'lomb' in a publication use:

Ruf, T. (1999) The Lomb-Scargle Periodogram in Biological Rhythm Research: Analysis of Incomplete and Unequally Spaced Time-Series. Biol. Rhythm Res. 30: 178-201

Corresponding BibTeX entry:

  @Article{,
    title = {The Lomb-Scargle Periodogram in Biological Rhythm
      Research: Analysis of Incomplete and Unequally Spaced
      Time-Series},
    author = {T. Ruf},
    journal = {Biological Rhythm Research},
    year = {1999},
    volume = {30},
    pages = {178-201},
  }