To cite the osmar package use:

Manuel J. A. Eugster and Thomas Schlesinger. osmar: OpenStreetMap and R. R Journal, 2012. Accepted for publication on 2012-08-14. http://osmar.r-forge.r-project.org/RJpreprint.pdf

Corresponding BibTeX entry:

  @Article{,
    title = {osmar: OpenStreetMap and R},
    author = {Manuel J. A. Eugster and Thomas Schlesinger},
    journal = {R Journal},
    year = {2010},
    note = {Accepted for publication on 2012-08-14},
    url = {http://osmar.r-forge.r-project.org/RJpreprint.pdf},
  }