To cite package 'metap' in publications use:

Michael Dewey (2019). metap: meta-analysis of significance values. R package version 1.1.

Corresponding BibTeX entry:

  @Manual{,
    title = {{metap}: meta-analysis of significance values},
    author = {Michael Dewey},
    year = {2019},
    note = {R package version 1.1},
  }