Sentence:  A moment's thought convinces us of the following: / "The <WSD>Cartesian product</WSD> of two Riemannian Einstein metrics with the same constant Ricci scalar ρ is again Ricci-constant, and has <font face="Minion" size=+1>Ric</font> = ρ." 
Meaning of the word marked with <WSD> tags:  The set of points in an (m + n)-dimensional Cartesian space corresponding to all possible pairs of points from the two sets from spaces of dimension m and n. Notation:  X \times Y = \{ (x_1, ... x_m, y_1, ... y_n) \| (x_1, ... x_m)\in X \land (y_1, ... y_n)\in Y \}.