Plain TeX, 2 figures autogenerated as blz1.ps and blz2.ps, 50.000 K, 
10 pages. Use a postscript printer and compile into postscript with DVIPS. 
This is a reprint of a 1972 preprint that was never published, but which 
is occasionally quoted and requested to me. If one does not use a
postscript printer the figures cannot be printed: the paper can still be
printed provided one changes the parameter \driver on line 3 from 1 to
5. The figures can be found in ref. [11] or [12].
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