To cite zoo in publications use:
Zeileis A, Grothendieck G (2005).“zoo: S3 Infrastructure for Regular and Irregular Time Series.”Journal of Statistical Software,14(6), 1–27.doi:10.18637/jss.v014.i06.
Corresponding BibTeX entry:
@Article{, title = {zoo: S3 Infrastructure for Regular and Irregular Time Series}, author = {Achim Zeileis and Gabor Grothendieck}, journal = {Journal of Statistical Software}, year = {2005}, volume = {14}, number = {6}, pages = {1--27}, doi = {10.18637/jss.v014.i06}, }