On Wed, 1 Dec 1999, Kurt Ewald wrote:
I read the sentence
" H is a subgroup fixing two letters and H is inverted by an Element of
order 2 in PSL(2,q)"
What does mean "H is inverted by an Element"
perhaps the explanation is possible in German.
H is cyclic group of order (q-1)/2 (q odd) or q-1 (q even).
Thus, "inverting H" most probably means inverting a generator of H.
This "Element" then sends each element of H to its inverse.