Addisson Salazar Jorge Igual Luis Vergara Arturo Serrano Learning Hierarchies from ICA Mixtures. 2271-2276 2007 IJCNN http://dx.doi.org/10.1109/IJCNN.2007.4371312 conf/ijcnn/2007 db/conf/ijcnn/ijcnn2007.html#SalazarIVS07