For model nos. 585 and 587:
Scarsella collection, Italy
Thence by descent
Acquired from the above by the present owner
For model no. 444:
Fulvio Ferrari, Turin
Acquired from the above by the present owner, 1980s
'Ceramiche a colaggio, per la serie', Domus, no. 422, January 1965, p. 54 for a similar example
Fernanda Pivano, 'Ettore Sottsass, Ceramiche dal 1955 al 1970', Domus, no. 749, May 1993, p. 70 for similar examples
Fulvio Ferrari, Ettore Sottsass Tutta la Ceramica, Turin, 1996, p. 99, figs. 377, 380, p. 100, figs. 385-86 for similar examples