By N.B. Grace
By Unknown, Alice Alfonsi
By Anna Claybourne
By Martine Agassi, Marieka Heinlen, Marieka Heinlen
By Campbell, Joan, Patrick, Sue
By Mary James
By Duncan Watts
By Michellejoy Hughes
By Percival, Tom, Percival, Tom
By Pease, Allan, Pease, Barbara
By Perry, Linda
By Sasha Fenton
By Kate Harrison
By David Scarfe
By Vorderman, Carol
By Henry Brook
By Holly Bourne
By Keane, Francine
By Frankel, Bethenny
By Brian, Kate
By Hesiod, Homer
By National Geographic Society (U. S.)
By Buchholz, Rachel, National Geographic Kids
By Emily Kreiger
By Murphy Ph.D., Dr. Joseph
By Law, Stephen, Postgate, Daniel
By Parry, Robert
By Neill, Trevor Johnson And Hugh
By Liz Pryor