Investigations on T violation and CPT symmetry in the neutral kaon   system -- a pedagogical approach --
  During the recent years experiments with neutral kaons have yielded remarkably sensitive results which are pertinent to such fundamental phenomena as CPT invariance (protecting causality), time-reversal invariance violation, coherence of wave functions, and entanglement of kaons in pair states. We describe the phenomenological developments and the theoretical conclusions drawn from the experimental material. An outlook to future experimentation is indicated. 
Maria Fidecaro (1), Hans-Juerg Gerber (2) ((1) CERN, Geneva, (2) ETH,   IPP, Zurich)