a production of WGBH Boston and WITF, Harrisburg; produced by Beth Hager and Randall MacLowry ; written by Ken Emerson and Randall MacLowry ; director, Randall MacLowry
an Invision Productions Limited production in association with Heights Productions, Inc. and WGBH Boston, with the assistance of Lion Television Limited ; produced and directed by William Cran ; written by William Cran, Daniel Yergin ; executive producer, Michael Sullivan
a PBS digital presentation ; a Gemini Productions film for the WGBH/Nova Science Unit and Clear Blue Sky Productions ; written and directed by Gail Willumsen ; produced by Jill Shinefield, Gail Williamson