written, produced and directed by Mark Davis ; a NOVA production by MDTV Productions for WGBH/Boston in association with National Geographic Channel International
a BBC/WGBH Boston/ProSieben co-production [in association with France 3 ; produced and directed by John Hayes Fisher ; produced for Nova by Gary Glassman ; senior executive producer, Paula S. Apsell
a co-production of Dentsu Inc. in association with David Rubinson and Creative Production Group, LLC ; written and directed by Robert Kirk ; produced by Diane Estelle Vicari
a Blakeway Production for the BBC and WGBH Boston ; produced by Chris Oxley & Malcolm Neum ; directed by Chis Oxley ; produced for NOVA by Joseph McMaster ; narration written by Joseph McMaster
a Nova production by Green Umbrella Ltd. for WGBH/Boston in association with BBC-TV and Sveriges Television ; produced by Peter Jones and Thomas Levenson ; written by Thomas Levenson ; directed by Peter Jones
produced by Swedish Television in association with WGBH Boston ; directors and producers, Bo G. Erikson, Carl O. Lofman ; for NOVA, written and produced by Bebe Nixon