@incollection{str:05:unilog:update,
author = "Lutz Stra{\ss}burger",
title ="What is a logic, and what is a proof?",
booktitle =   {Logica Universalis},
publisher =   {Birkh\"auser},
pages =       {135--145},
editor =      {Jean-Yves Beziau},
year = 2005,
note ="Updated version at 
http://www.lix.polytechnique.fr/\~{ }lutz/papers/WhatLogicProof.pdf",
}