共 20 条
[1]
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[2]
BABCOCK SH, 1945, Patent No. 2375885
[3]
BERGEL F, 1947, Patent No. 2423062
[5]
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[6]
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[7]
Flint R. B., 1935, U.S. Patent, Patent No. [US2016962, 2016962]
[8]
HARRIS SA, 1943, Patent No. 2319545

