This ring is part of a group of five developed between the years 1987 and 1990. Three of these are part of the collection of the Museum of Modern Art in Arnhem (NL). Pubblications: Schmuckszene, catalogue n.39, Munich 1987, pag.17; Novidades de Holanda - News from the Netherlands, catalogue Lisbona 1990, pag.34-35; Article in Art Aurea n.2/1990, pag. 82-84, Marjan Unger - Performance fur Portugal; Op het huid/ Gioielli della collezione permanente del Museo di Arte Moderna di Arnhem (NL), Catalogue Arnhem 2000, pag.131-132; Zonder wrijving geen glans, pamphlet from the exhibition in the Utrecht CentralMuseum in 2002; Padova e il suo territorio, rivista 180, April 2016, pag.35.