BBC Monograph no 5downloads.bbc.co.uk/rd/pubs/archive/pdffiles/monographs/...rings of black spots,...
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BBC Monograph no 5downloads.bbc.co.uk/rd/pubs/archive/pdffiles/monographs/...rings of black spots, one for 45 r.p.m., and one for 331 r.p.m. which, as can be seen in Fig. 1, are carried