Related literature and comparable objects: Avelino Texeira da Mota: Descoberta de bronze Antigos. In: Boletim Cultural da Guiné Portuguesa, vol. 15, Lisbon,1960, p. 625-632 / Sono with bar and attachment, Museo indentation Civiltà, formerly Museo Nazionale Preistorico ed Etnografico (Museo Luigi Pigorini), Rome, inv. no. 30869 / Sono-attachment without bar, auction: African, Oceanic and Pre-Columbian Art. New York, Sotheby's, 14.10.2010, cat. no. 119, published in: Ezio Bassani: Sono from Guinea Bissau. In: African Arts, vol. 12, no. 4, San Francisco, 1979, p. 47, ill. 7.

Maurice Bonnefoy (1920–1999), New York / 1962 Ernst Winizki (1915–1997), Zurich / collection Wally and Udo Horstmann, Zug / Private Collection, Switzerland

Die Kunst von Schwarz-Afrika. Zurich, Kunsthaus Zurich, 1970/71, cat. no. E16, p. 86f, ill. p. 87 / Masters of African Art. Forms and Styles. Eighty-four Sculptures from the Horstmann Collection. Mendrisio, Museo d'arte, 2007, cat. no. 5, p. 43, , with ill.

Ezio Bassani: Sono from Guinea Bissau. In: African Arts, vol. 12, no. 4, San Francisco, 1979, p. 46f., ill. 3, ill. p. 45 / Karl-Ferdinand Schaedler: Erde und Erz. 2500 Jahre Afrikanische Kunst aus Terrakotta und Metall. Munich, 1997, cat. no. 2, p. 15f., ill. p. 14 / Ezio Bassani and Michael Bockemühl: The Power of Form. African Art from the Horstmann Collection. Mailand, 2002, cat. no. 1, p. 34, ill. p. 35