“…Hence, if we look for a new λ -product • λ which is compatible in the sense of (5.12), then this means that the new λ -product • λ is a 2-cocycle of the original associative conformal algebra. If our algebra is, for instance, the current conformal algebra Cur n or the conformal algebra Cend n , it is proved in [22] that the second cohomology group of Cend n and Cur n with coefficients in any conformal bimodule is trivial, hence our λ -product • λ has to be a coboundary, namely, of the form • N λ for some N. This means that we have not much freedom and, looking for compatible associative λ -products, we must, in principle, work with Nijenhuis operators.…”