"Stephen Hawking dies aged 76" http://www.bbc.com/news/uk-43396008 "Obituary: Stephen Hawking" http://www.bbc.com/news/science-environment-15555565 "Stephen Hawking, modern cosmology's brightest star, dies aged 76" https://www.theguardian.com/science/2018/mar/14/stephen-hawking-professor-dies-aged-76 "Stephen Hawking obituary" https://www.theguardian.com/science/2018/mar/14/stephen-hawking-obituary /tvb http://www.leapsecond.com/great2016a/