Evolution and Testing of the Lacunar Hypothesis" by Bamford and Warlow in this issue of Stroke reviews many important aspects of these unique pathologic vascular lesions. I concur with the authors' emphasis on the need to maintain homogeneity in the classification of stroke conditions, specifically lacunes. A stroke classification scheme would ideally be based on 1) risk factor profile such as ...

We survey the recent applications and developments of sieve methods related to discrete groups, especially in the case of infinite index subgroups of arithmetic groups.