1. Levy, L. F., Subarachnoid haemorrhage without arteriographic vascular abnormality. J. Neurosurg.17 (1960), 252–258.
2. Krayenbühl, H., Yaşargil, G., L'anéurisme cérébral. Series Chirurgia n. 4, p. 65. Basle: Geigy.
3. Sahs, L. A., Perret, G. E., Locksley, H. B., Nishioka, H., Intracranial aneurysms and subarachnoid haemorrhage. A cooperative study, p. 224. Philadelphia-Toronto: J. B. Lippincott Co. 1972.