M. Llanos Tobarra Diego Cazorla Fernando Cuartero Gregorio Díaz Analysis of Web Services Secure Conversation with Formal Methods. 27 2007 ICIW http://doi.ieeecomputersociety.org/10.1109/ICIW.2007.17 conf/iciw/2007 db/conf/iciw/iciw2007.html#TobarraCCD07