“…Lehman [35] improved this last upper bound considerably by showing that exists a number x 0 with x 0 < 1.65 × 10 1165 such that π(x 0 ) > li(x 0 ). After some further improvements (see, for instance, te Riele [55], Bays and Hudson [7], Chao and Plymen [15], Saouter and Demichel [51], Stoll and Demichel [54] and Saouter, Trudgian, and Demichel [50]), the current best upper bound was found by Platt and Trudgian [42]. They proved that there exists a number x 0 with x 0 < e 727.951332668 such that π(x 0 ) > li(x 0 ).…”