Possible Pre-Seismic Indications Prior to Strong Earthquakes That Occurred in Southeastern Mediterranean as Observed Simultaneously by Three VLF/LF Stations Installed in Athens (Gr... oleh Dimitrios Z. Politis, Stelios M. Potirakis, Sudipta Sasmal, Filopimin Malkotsis, Dionisis Dimakos, Masashi Hayakawa