Phillip Helbig
"The delta theta-z_s relation as a cosmological test"*
in Proceedings of the twelfth Potsdam Cosmology Workshop (ADS: 1998lsst.conf.....M)
V. Müller, St. Gottlöber, J. P. Mücket & J. Wambsganß (eds.)
Singapore, World Scientific, pp. 319–320 (1998)
ISBN 981-023499-6
ADS: 1998lsst.conf..319H | Google Scholar