+ We have corrected lines 402-405 (now lines 419-422) as follows:
+ ``For all those feedforward network topologies and all outputs the
+ obtained results for the non-chaotic case outperform the chaotic
+ ones. Finally, the rates for the strategies show that the different
+ feedforward networks are unable to learn them.'' More generally, in
+ the whole paper the term feedforward has been added, when needed, to
+ clarify our discussion.