@ARTICLE{espsurvey, author = {{Esponda}, F.}, title = "{Negative Surveys}", journal = {ArXiv Mathematics e-prints}, eprint = {math/0608176}, year = 2006, month = aug, adsurl = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006math......8176E&db_key=PRE} }