“…A symmetric (0, 2)-tensor E on M is called Riemann compatible or R-compatible [59,60] (see also [30]) if on M we have R(EX 1 , X, X 2 , X 3 ) + R(EX 2 , X, X 3 , X 1 ) + R(EX 3 , X, X 1 , X 2 ) = 0, for all X, X 1 , X 2 , X 3 ∈ χ(M ), where E is the endomorphism on χ(M ) defined as…”