International Symposium on the Origin and Distribution of the Elements L.H.Ahrens, (London)International Symposium on the Origin and Distribution of the Elements (Wash.)International Symposium on the Chemistry of Cement (Cologne)International Symposium on the Classification of Brain Tumours International Symposium on the Chemistry of Cement International symposium on the electrophysiology of the heart International Symposium on the Classification of Brain Tumours The Fifth International Symposium on the Chemistry of Cement Collection of international symposium on conservation of historical cities and buildings