Kahle D, Wickham H (2013).“ggmap: Spatial Visualization with ggplot2.”The R Journal,5(1), 144–161.https://journal.r-project.org/archive/2013-1/kahle-wickham.pdf.
Corresponding BibTeX entry:
@Article{, author = {David Kahle and Hadley Wickham}, title = {ggmap: Spatial Visualization with ggplot2}, journal = {The R Journal}, year = {2013}, volume = {5}, number = {1}, pages = {144--161}, url = {https://journal.r-project.org/archive/2013-1/kahle-wickham.pdf}, }