Knitting a sock leg on two circular needles - YouTube
2 At-A-Time Socks: The Secret of Knitting Any Two Socks at Once, on Just One Circular Needle!: Amazon.co.uk: Morgan-Oakes, Melissa: 9780715329559: Books
2 Socks on 2 Circular Needles (knit) - TBD
Knit Your Socks On Straight: A New and Inventive Technique with Just Two Needles: Amazon.co.uk: Alice Curtis: 0884863356920: Books