共 18 条
[11]
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[12]
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[13]
1949, Patent No. 2483487
[14]
1960, Patent No. 1139104
[15]
1966, Patent No. 1050502
[16]
1965, Patent No. 987335
[17]
1964, Patent No. 960507
[18]
1963, Patent No. 937458