Published in Nautilus, in 1992, in volume 106, pages 39-42

Published in Nautilus, in 1992, in volume 106, pages 43-49

Published in Nautilus, in 1992, in volume 106, pages 50-54

Published in Nautilus, in 1992, in volume 106, pages 55-59

Published in Nautilus, in 1992, in volume 106, pages 68-71

Published in Nautilus, in 1992, in volume 106, pages 76

Published in Nautilus, in 1992, in volume 106, pages 77-114

Published in Nautilus, in 1992, in volume 106, pages 115-118

Published in The Nautilus, in 1992, in volume 106, issue 1, pages 24-38