Let A and B be any sets. Then the product of left bracketing bar A right bracketing bar and left bracketing bar B right bracketing bar is defined as the Cartesian product left bracketing bar A right bracketing bar * left bracketing bar B right bracketing bar = left bracketing bar A×B right bracketing bar (Ciesielski 1997, p. 68; Dauben 1990, p. 173; Moore 1982, p. 37; Rubin 1967, p. 274; Suppes 1972, pp. 114-115).