Giovanni F. Bignami. The Mystery of the Seven Spheres: How Homo sapiens will Conquer Space. Springer. 2015. ISBN 9783319170046., Page 110 (页面存档备份,存于互联网档案馆)
Giovanni F. Bignami. The Mystery of the Seven Spheres: How Homo sapiens will Conquer Space. Springer. 2015. ISBN 9783319170046., Page 110 (页面存档备份,存于互联网档案馆)