Number | Date | Country | Kind |
---|---|---|---|
59-227766 | Oct 1984 | JPX |
Number | Name | Date | Kind |
---|---|---|---|
4245191 | Schroeder | Jan 1981 | |
4583095 | Peterson | Apr 1986 |
Entry |
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Arai et al., "An Undergrond Radar System"; Trans. of the Institute of Electronics and Communications Engineering; (6/83, vol. J66-B, No. 6; pp. 713-719). |
Suzuki et al.; "Underground Radar System"; Sane; (vol. 79, No. 220, 1/25/80; pp. 21-28). |