Our aim is to publish papers of interest to a wide mathematical audience, such as expository articles that make research results more widely accessible, and papers on topics with fairly broad appeal. Main articles must be written in such a way that a research student interested in the topic of the paper can read them profitably. Mathematical notes can be at a slightly higher level. Clarity of exposition, accuracy of details and the relevance and interest of the subject matter will be the decisive factors in our acceptance of an article for publication. All papers are refereed.