See Butler, op. cit., pl. XVI, 158 and 222 for examples of both models in the Hermitage and the Boucher engraving upon which the group is based. Also see L. and Y. Adams, op. cit., p. 176 and 179; Berling, op. cit., p. 55 (the single figure); and Menzhausen, op. cit., p. 165 (the group).