To cite MixMAP in publications use:

Gregory J. Matthews, Andrea S. Foulkes (2015). MixMAP: An R Package for Mixed Modeling of Meta-Analysis $p$ Values in Genetic Association Studies. Journal of Statistical Software, Code Snippets, 66(3), 1-11. URL http://www.jstatsoft.org/v66/c03/.

Corresponding BibTeX entry:

  @Article{,
    title = {{MixMAP}: An {R} Package for Mixed Modeling of
      Meta-Analysis $p$ Values in Genetic Association Studies},
    author = {Gregory J. Matthews and Andrea S. Foulkes},
    journal = {Journal of Statistical Software, Code Snippets},
    year = {2015},
    volume = {66},
    number = {3},
    pages = {1--11},
    url = {http://www.jstatsoft.org/v66/c03/},
  }