Philippe Balbiani Alexandru Baltag Hans P. van Ditmarsch Andreas Herzig T. Hoshi Tiago De Lima What can we achieve by arbitrary announcements?: A dynamic take on Fitch's knowability. 42-51 2007 TARK http://doi.acm.org/10.1145/1324249.1324259 conf/tark/2007 db/conf/tark/tark2007.html#BalbianiBDHHL07