To cite package ‘photobiologySunCalc’ in publications use:

  Aphalo, Pedro J. (2015) The r4photobiology suite. UV4Plants Bulletin,
  2015:1, 21-29. DOI:10.19232/uv4pb.2015.1.14

A BibTeX entry for LaTeX users is

  @Article{,
    author = {Pedro J. Aphalo},
    title = {The r4photobiology suite},
    journal = {UV4Plants Bulletin},
    volume = {2015},
    number = {1},
    pages = {21-29},
    year = {2015},
    doi = {10.19232/uv4pb.2015.1.14},
  }