Just about all banjo players make an attempt at imitating his three finger picking style. He is most likely mentioned in every book about banjo's and he is most certainly mentioned in every book about blue grass.
Earl recorded as recently as 2009 on Steve Martins, Grammy winning, album The Crow. He can be heard, appropriately on the song Daddy Played the Banjo. He was approximately 85 years old at the time.
I have added a few links to some youTube videos of Earl on My links page