LEADER 00000nam 2200181 a 4500 001 0451784 003 UkHlHU 007 t 008 000311 1 1929 000 eng 040 UkHlHU 050 4 QC 715 C1 100 0 Campbell, H.R. 245 00 Photoelectric cells. 300 0000p. 700 0 Ritchie D. 946 260 lacks |a 946 260 lacks |b 946 260 lacks |c, 008 has valid date 946 300 data invalid 946 6XX absent
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