Gudmund Skovbjerg Frandsen Piotr Sankowski Dynamic Normal Forms and Dynamic Characteristic Polynomial. 434-446 2008 ICALP (1) http://dx.doi.org/10.1007/978-3-540-70575-8_36 conf/icalp/2008-1 db/conf/icalp/icalp2008-1.html#FrandsenS08