14. Acknowledgments
     The author is indebted to Sean Brennan, Rupert Perera and John Hubbell 
for provision of the latest versions of the databases involved and for 
helpful discussions, without which this could not have been pursued. He is 
also happy to acknowledge discussions with A. Caticha and support from 
the Lindemann fellowship and the English Speaking Union of the Commonwealth, 
and particularly NIST and the Quantum Metrology Division.
 
 
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