Firewall Wizards: Help with SPF

["Marcelo Barbosa Lima" <marcelo.lima () dcc unicamp br>]

   Hi folks,

        I am studing SPFs (Theorical purposes and concepts) and i'd like to know
if someboby can help me with pointers, references and papers about this
subject. I am specially interested in stuff about services and protocols
support using SPF, Proxy vs. SPF, SPF implementation, etc.  
Thanks and sorry for my poor english :-) !


                                Marcelo Barbosa Lima
                                   marcelo.lima () dcc unicamp br
                                      Mestrado em Ciencia da Computacao