The B series, consisting of roughly 220 reports, began in 1953 and reports were added to it until 1980. However from the early 1970s the numbers issued in this series declined markedly.
The reports were subsequently placed in the mainstream Ordinary (O) series which covers fundamental research and instrumentation. There is also some overlap between the subject content of the B reports and the Theoretical Physics Notes, a series which began slightly later on.
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