  The rich variety of phase transitions observed in the strained p-SiGe system
are considered and compared. It is shown that the integer quantum Hall effect
transitions, the Hall insulating transition and the re-entrant transition into
an insulating phase near filling factor 3/2 are all very similar and good
examples of quantum critical phase transitions. The B=0 metal insulator
transition also shows many similarities to these transitions but requires the
inclusion of an extra impurity scattering term to fully explain the data.
