[en] By performing the one-sided Laplace transform on the scalar integro-differential equation for a semi-infinite plane-parallel isotopic scattering atmosphere with a scattering albedo ω₀<=1, an integral equation for the emergent intensity has been derived. Application of the Wiener-Hopf technique to this integral equation will give the emergent intensity. The intensity at any optical depth for a positive scattering angle is also derived by inversion. The intensity at any optical depth for a negative scattering angle is also derived in terms of Cauchy's principal value using Plemelj's formulae. (Auth.)