"We were drawn like moths to a flame": folk singer Arlo Guthrie looks back on Woodstock

Arlo Guthrie was in his early twenties when he played on the first day of Woodstock festival, which is celebrating its 50th anniversary this weekend. The now 72-year-old singer - son of folk music revolutionary Woody Guthrie - looks back at the legendary festival, and the generation that made it happen.