Tina Jørstian and Poul Eric Munk Nielsen, eds., Light Years Ahead, The Story of the PH Lamp, Copenhagen, 1994, pp. 147-49, 200 for similar examples
Charlotte and Peter Fiell, eds., 1000 Lights, Vol. 1: 1879 to 1959, Cologne, 2005, p. 240 for a similar example