Nicholas Kolokotronis Konstantinos Limniotis Nicholas Kalouptsidis Improved Bounds on the Linear Complexity of Keystreams Obtained by Filter Generators. 246-255 2007 Inscrypt http://dx.doi.org/10.1007/978-3-540-79499-8_20 conf/cisc/2008 db/conf/cisc/inscrypt2008.html#KolokotronisLK08