共 20 条
[1]
Cooley JF, 1902, Patent, Patent No. [692631, 692,631]
[3]
Formhals A, 1934, United States patent US, Patent No. 1975504
[5]
GILBERT W, LOADSTONE MAGNETIC B, P1600
[6]
Groitzsch D., 1986, US Patent, Patent No. [4,618,524, 4618524]
[7]
HERMANS PH, 1946, CONTRIBUTIONS PHYSIC
[9]
How T. V., 1985, U.S. Patent, Patent No. [US4,552,707A, 4552707, US 4552707]