To cite CircNNTSR in publications use:

Juan Jose Fernandez-Duran, Maria Mercedes Gregorio-Dominguez (2016). CircNNTSR: An R Package for the Statistical Analysis of Circular, Multivariate Circular, and Spherical Data Using Nonnegative Trigonometric Sums. Journal of Statistical Software, 70(6), 1-19.<doi:10.18637/jss.v070.i06>

Corresponding BibTeX entry:

  @Article{,
    title = {{CircNNTSR}: An {R} Package for the Statistical Analysis
      of Circular, Multivariate Circular, and Spherical Data Using
      Nonnegative Trigonometric Sums},
    author = {Juan Jos\'e Fern\'andez-Dur\'an and Mar\'ia Mercedes
      Gregorio-Dom\'\inguez},
    journal = {Journal of Statistical Software},
    year = {2016},
    volume = {70},
    number = {6},
    pages = {1--19},
    doi = {10.18637/jss.v070.i06},
  }