Occlusion Culling Methods. - Heinrich Hey; Werner Purgathofer (Eurographics (State of the Art Reports), 2001)

Real-Time Occlusion Culling with a Lazy Occlusion Grid. - Heinrich Hey; Robert F. Tobler; Werner Purgathofer (Rendering Techniques, 2001)

Importance sampling with hemispherical particle footprints. - Heinrich Hey; Werner Purgathofer (SCCG, 2002)

Advanced Radiance Estimation For Photon Map Global Illumination. - Heinrich Hey; Werner Purgathofer (Comput. Graph. Forum, 2002)