The Artist's Handlist, 1937, no. 136 (qu 16) Karl Nierendorf (ed.), Paul Klee, Paintings, Watercolors, 1913 to 1939, New York, 1941, illustrated pl. 55; Rosamund Frost, 'Klee: Pigeons Come Home to Roost', in Art News, vol. 41, June-July 1942, illustrated p. 25; Will Grohmann, Paul Klee, Geneva & Stuttgart, 1954, no. 366, illustrated p. 294; Jürg Spiller (ed.), Paul Klee. Das bildnerische Denken. Form- und Gestaltungslehre, Basel & Stuttgart, 1956, mentioned p. 517; Ellen Marsh, 'Paul Klee and the Art of Children', in College Art Journal, vol. 16, no. 2, Winter 1957, illustrated p. 145; Gualtieri di San Lazzaro, Klee. A Study of his Life and Work, London, 1957, no. 122, illustrated p. 276; Max Huggler, Paul Klee. Die Malerei als Blick in den Kosmos, Frauenfeld & Stuttgart, 1969, p. 163; Jürg Spiller (ed.), Paul Klee. Unendliche Naturgeschichte. Prinzipielle Ordnung der bildnerischen Mittel verbunden mit Naturstudium, und konstruktive Kompositionswege. Form- und Gestaltungslehre, Basel & Stuttgart, 1970, illustrated p. 204; Rainer Crone & Joseph Leo Koerner, Paul Klee. Legends of the Sign, New York, 1991, illustrated fig. 7; Paul Klee Foundation (ed.), Paul Klee, Catalogue raisonné, Bern, 2003, vol. 7, no. 7072, illustrated p. 261; illustrated in colour p. 286