Lorenzo BettiniSara CapecchiMariangiola Dezani-CiancagliniElena GiachinoBetti VenneriDeriving session and union types for objects.1163-1219201323Math. Struct. Comput. Sci.6https://doi.org/10.1017/S0960129512000886db/journals/mscs/mscs23.html#BettiniCDGV13