Benedetto Intrigila Richard Statman The Omega Rule is P<sub>1</sub><sup>1</sup>-Complete in the <i>lambdabeta</i> -Calculus. 178-193 2007 conf/tlca/2007 TLCA http://dx.doi.org/10.1007/978-3-540-73228-0_14 db/conf/tlca/tlca2007.html#IntrigilaS07