Henri Habrias Pascal Poizat Jean-Yves Lafaye A Study of Collaborative Work: Answers to a Test on Formal Specification in B. 1856-1857 1999 conf/fm/1999-2 World Congress on Formal Methods http://link.springer.de/link/service/series/0558/bibs/1709/17091856.htm db/conf/fm/fm1999-2.html#HabriasPL99