Amos Beimel Yuval Ishai Eyal Kushilevitz General constructions for information-theoretic private information retrieval. 213-247 2005 71 J. Comput. Syst. Sci. 2 http://dx.doi.org/10.1016/j.jcss.2005.03.002 db/journals/jcss/jcss71.html#BeimelIK05