To cite package 'aws.polly' in publications use:

Thomas J. Leeper (2016). aws.polly: An R Packge. R package version 0.1.2.

Corresponding BibTeX entry:

  @Manual{,
    title = {aws.polly: An R Package},
    author = {Thomas J. Leeper},
    year = {2016},
    note = {R package version 0.1.2},
  }