In ([150*], p. 142), Einstein used the same symbol (here called ) for a different tensor equally denoted in
his previous paper [147*], which he now named ([150*], p. 141), and which here is (cf. Section 2.3.2, Eq. (75)).
Worse, in the 4th Princeton edition of The Meaning of Relativity ([156*], p. 140), the notation now corresponded to
.