Henkin sentences

A Henkin Sentence proves it own provability. I can not seem to find some good examples though.

 

[ http://www3.law.columbia.edu/hrlr/hrlr_journal/42.1/Rosenblum.pdf ]

[ http://www.jstor.org/pss/2273791 ]

[ http://phil.gu.se/logic/uppsatser/blanck_logd.pdf ]