Declare matrix with real elements



Dear all,

in my Maxima code I need a matrix M of real parameters:

declare(M, nonscalar);
done

Then I use such real parameters, for example:

x : conjugate(M[1,1]);
conjugate(M[1,1])

How can I tell Maxima that all the elements of M are real, such that
conjugate(M[i,j]) = M[i,j] for any i,j?

Thank you in advance,

Michele