Spherical Gaussian approximation for Blinn-Phong, Phong and Fresnel | Sébastien Lagarde
Simon's Tech Blog: Microfacet BRDF
Alex Ameye on Twitter: "Added importance sampling for microfacet distribution functions, looks great. Beckmann left, blinn-phong right, using data from measured materials. https://t.co/TWTJUZmeBY" / Twitter
cycles render engine - What do glossy distribution models do? - Blender Stack Exchange