Reza Asvadi Amir H. Banihashemi Mahmoud Ahmadian-Attari Design of irregular quasi-cyclic protograph codes with low error floors. 908-912 2011 ISIT https://doi.org/10.1109/ISIT.2011.6034270 conf/isit/2011 db/conf/isit/isit2011.html#AsvadiBA11