EP 415850, Wierzbicki, Michel; Bonnet, Jacqueline & Brisset, Martine et al., "Bivalent metal salts of 2-N,N-di(carboxymethyl)amino,3-cyano,4-carboxymethyl,5-carboxy-thiophene-acid, process for their preparation and pharmaceutical compositions containing them", published 1991-03-06, assigned to Adir & Co.
