VLBI phase referencing at 5 degrees separation Elósegui, P. ; Marcaide, J. M. ; Alberdi, A. ; Ratner, M. I. ; Shapiro, I. I. ; Quirrenbach, A. ; Witzel, A. ; Mantovani, F. ; Rius, A. Abstract Publication: Sub-arcsecond Radio Astronomy Pub Date: 1993 Bibcode: 1993sara.conf..412E