Cone Beam Single Photon Emission Computed Tomography Using Two Orbits. - R. Clack; Gengsheng L. Zeng; Y. Weng; Paul E. Christian; Grant T. Gullberg (IPMI, 1991)

Toward Accurate Attenuation Correction in SPECT Without Transmission Measurements. - Andy Welch; R. Clack; Frank Natterer; Grant T. Gullberg (IEEE Trans. Medical Imaging, 1997)