Proceedings of the Particle Physics and Early Universe Conference (PPEUC). For this paper: postscript PPEUC CMB index 1 Introduction.. ... Observatoire de Strasbourg , 11, rue de l'Universit?, ... We discuss the implications of two possible, recent Sunyaev--Zel'dovich (SZ) detections for which no optical or X-ray counterparts have been found. This suggests that the objects reside at high redshift, which is difficult to reconcile with a critical cosmology. ... Fri Jul 25 11:32:28 BST 1997 ...