@unpublished{iu2007,
 author = {J. M. Siskind},
 title = {Automatic Differentiation of Functional Programs or Lambda the
          Ultimate Calculus or How I Learned to Stop Worrying and Love
	  Map-Closure},
 location = {Indiana University},
 date = 20,
 month = feb,
 year = 2007,
 url = {http://engineering.purdue.edu/~qobi/tweet-talks/iu2007-slides.pdf}}