Harmonic-free single-crystal monochromators for neutrons and X-rays

In Hart & Rodrigues [J. Appl. Cryst. (1978), 11, 248–253] equation (6) should read I_{p(m + n)h}(α) = ∫^∞_−∞ Π^{l = m + n − 1}_{l = 0} R_⊥ph(θ − lα)dθ + ∫^∞_−∞Π^{l = m + n − 1}_{l = 0} R_||ph(θ − lα)dθ. The equation given is correct for the double reflection case and therefore the error does not propagate in the paper.