Analysis of creatine kinase activity in 504 patients with proximal spinal muscular atrophy types I - III from the point of view of progression and severity. - Rudnik-Schoneborn,S.; Lutzenrath,S.; Borkowska,J.; Karwanska,A.; Hausmanowa-Petrusewicz,I.; Zerres,K. (Eur Neurol, 1998)