Paper  bibtex   

@Article{ss06,
  Author         = {David Steiner and Thomas Strahm},
  Title          = {On the proof theory of type two functionals based on
                   primitive recursive operations},
  Journal        = {Mathematical Logic Quarterly},
  Volume         = {52},
  Number         = {3},
  Pages          = {237{--}252},
  url            = {2006/ss06.pdf},
  year           = 2006
}