Stefan Hetzl Alexander Leitsch Daniel Weller Bruno Woltzenlogel Paleo Herbrand Sequent Extraction. 462-477 2008 AISC/MKM/Calculemus http://dx.doi.org/10.1007/978-3-540-85110-3_38 conf/aisc/2008 db/conf/aisc/aisc2008.html#HetzlLWP08