Well, just for the record, it's working like a charm now! Maybe some improvements are possible, but it suits me. Thank you all!
Code:
class AdvancedUserRecipe1313445974(BasicNewsRecipe):
title = u'International Viewpoint 4'
oldest_article = 90
max_articles_per_feed = 100
feeds = [(u'Articles', u'http://www.internationalviewpoint.org/spip.php?page=backend')]
def print_version(self, url):
return url.replace('http://www.internationalviewpoint.org/spip.php?article', 'http://www.internationalviewpoint.org/spip.php?page=print_article&id_article=')