url(r'^changes/(?P<since>\d*(\.\d*)?)\.(?P<emitter_format>xml|json|yaml)$', changes_resource),
#url(r'^books/(?P<id>[\d,]+)\.(?P<emitter_format>xml|json|yaml)$', book_resource),
url(r'^changes/(?P<since>\d*(\.\d*)?)\.(?P<emitter_format>xml|json|yaml)$', changes_resource),
#url(r'^books/(?P<id>[\d,]+)\.(?P<emitter_format>xml|json|yaml)$', book_resource),