Howsun Jow and Vivek Gowri-Shankar carried out this
work as PhD students at Manchester University under the supervision of
Magnus Rattray. We gratefully acknowledge contributions to the design,
documentation and testing from Paul Higgs and Cendrine Hudelot. The
PHASE software was developed as part of a BBSRC funded research project
into RNA-based phylogenetic methods (investigators: Paul Higgs and Magnus
Rattray).