Reference:
  Author: Alexei Drummond and Korbinian Strimmer
  Title: "PAL: an object-oriented programming library for molecular evolution and phylogenetics"
  Journal: Bioinformatics
  Year: 2001
  Volume: 17
  Number: 7
  Pages: 662-663
  DOI: 10.1093/bioinformatics/17.7.662
  PMID: 11448888
  URL: http://bioinformatics.oxfordjournals.org/content/17/7/662.short
  eprint: http://bioinformatics.oxfordjournals.org/content/17/7/662.full.pdf+html
