Reference:
  Author: Melissa J. Hubisz and Katherine S. Pollard and Adam Siepel
  Title: "PHAST and RPHAST: phylogenetic analysis with space/time models"
  Journal: Bioinformatics
  Year: 2011
  Volume: 12
  Number: 1
  Pages: 41-51
  DOI: 10.1093/bib/bbq072
  PMID: 21278375
  URL: http://bib.oxfordjournals.org/content/12/1/41
  eprint: http://bib.oxfordjournals.org/content/12/1/41.full.pdf+html
