@inproceedings{popl2007b,
 author = {J. M. Siskind and
           B. A. Pearlmutter},
 title = {First-Class Nonstandard Interpretations by Opening Closures},
 booktitle = {Proceedings of the Annual Symposium on Principles of
              Programming Languages (POPL)},
 pages = {71-76},
 location = {Nice, France},
 day = {17--19},
 month = jan,
 year = 2007,
 url = {http://engineering.purdue.edu/~qobi/papers/popl2007b.pdf}}