idt-normalized Legendre polynomials up to
                 degree LMAX. Degree L corresponds to array index L+1.

       DP        (output) REAL*8, DIMENSION (LMAX+1)

                 An array of the first derivatives of the Schmidt-normalized
                 Legendre polynomials up to degree LMAX. Degree L corresponds
                 to array index L+1.

       LMAX      (input) INTEGER

                 The maximum degree of the Legendre polynomials to be
                 computed.

       Z         (i