New ephemeris of the ADC source 2A 1822–371: a stable orbital-period derivative over 30 years L. Burderi, T. Di Salvo, A. Riggio, A. Papitto, R. Iaria, A. D'Aì and M. T. Menna A&A, 515 (2010) A44 Published online: 08 June 2010 DOI: 10.1051/0004-6361/200912881