To cite the ouch package in publications use:

Aaron A. King and Marguerite A. Butler (2009), ouch: Ornstein-Uhlenbeck models for phylogenetic comparative hypotheses (R package), https://kingaa.github.io/ouch/

Butler, M. A. and King, A. A. (2004) Phylogenetic comparative analysis: a modeling approach for adaptive evolution Am. Nat. 164:683--695

As ouch is continually evolving, you may want to cite its version number. Find it with 'packageVersion("ouch")'.

Corresponding BibTeX entries:

  @Manual{,
    title = {ouch: Ornstein-Uhlenbeck models for phylogenetic
      comparative hypotheses},
    author = {Aaron A. King and Marguerite A. Butler},
    year = {2009},
    url = {https://kingaa.github.io/ouch/},
  }

  @Article{,
    author = {Marguerite A. Butler and Aaron A. King},
    title = {Phylogenetic comparative analysis: a modeling approach for
      adaptive evolution},
    journal = {American Naturalist},
    year = {2004},
    volume = {164},
    pages = {683--695},
    url = {http://www.press.uchicago.edu/ucp/journals/journal/an.html},
  }