To cite 'GuardianR' in publications use:

Bastos, M. T. Shares, Pins, and Tweets: News readership from daily papers to social media. Journalism Studies, 2014.

Corresponding BibTeX entry:

  @Article{,
    title = {Shares, Pins, and Tweets: News Readership from Daily
      Papers to Social Media},
    author = {Marco T. Bastos},
    journal = {Journalism Studies},
    publisher = {Routledge},
    year = {2014},
    issn = {1469-9699},
  }