| Original language | English |
|---|---|
| State | Published - 1987 |
| Event | Research and Exploration - Duluth, Minnesota, United States Duration: Jan 1 1987 → … |
| Original language | English |
|---|---|
| State | Published - 1987 |
| Event | Research and Exploration - Duluth, Minnesota, United States Duration: Jan 1 1987 → … |