I wonder if you fine categorists could help me track down an old preprint? Many people have written about probability distributions forming a monad (and so probabilistic computations can be captured as a "computational effect"). The reference trail goes back to Michele Giry, "A Categorical Approach to Probability Theory", LNM 915:68-85, 1981 and thence to F W Lawvere, "The Category of Probabilistic Mappings", preprint, 1962 I have Giry's paper, but can find no trace on the web of Lawvere's preprint. Does anyone know where I might find a copy? Might someone even have a copy that they would be prepared to scan? Thanks, Jeremy Jeremy.Gibbons@comlab.ox.ac.uk Oxford University Computing Laboratory, TEL: +44 1865 283508 Wolfson Building, Parks Road, FAX: +44 1865 283531 Oxford OX1 3QD, UK. URL: http://www.comlab.ox.ac.uk/oucl/people/jeremy.gibbons.html [For admin and other information see: http://www.mta.ca/~cat-dist/ ]