From the Daily DX:
ZK1CG, Victor Rivera, reports as of June 1, 2006 ZK1 stations will finally change to the new E51 prefix in the Cook Islands. On August 15, 2004 ITU Operational Bulletin No. 818 stated “Following a request from New Zealand, the International Call Sign Series E5A-E5Z, in accordance with the provisions of No. [...]
